[media] media/usb: fix kconfig dependencies

[media] media/usb: fix kconfig dependencies

(a.k.a. Kconfig bool depending on a tristate considered harmful)
Fix various build errors when CONFIG_USB=m and media USB drivers
are builtin.  In this case, CONFIG_USB_ZR364XX=y,
CONFIG_VIDEO_PVRUSB2=y, and CONFIG_VIDEO_STK1160=y.
This is caused by (from drivers/media/usb/Kconfig):
menuconfig MEDIA_USB_SUPPORT
	bool "Media USB Adapters"
	depends on USB && MEDIA_SUPPORT
	           =m     =y
so MEDIA_USB_SUPPORT=y and all following Kconfig 'source' lines
are included.  By adding an "if USB" guard around most of this file,
the needed dependencies are enforced.
drivers/built-in.o: In function `zr364xx_start_readpipe':
zr364xx.c:(.text+0xc726a): undefined reference to `usb_alloc_urb'
zr364xx.c:(.text+0xc72bb): undefined reference to `usb_submit_urb'
drivers/built-in.o: In function `zr364xx_stop_readpipe':
zr364xx.c:(.text+0xc72fd): undefined reference to `usb_kill_urb'
zr364xx.c:(.text+0xc7309): undefined reference to `usb_free_urb'
drivers/built-in.o: In function `read_pipe_completion':
zr364xx.c:(.text+0xc7acc): undefined reference to `usb_submit_urb'
drivers/built-in.o: In function `send_control_msg.constprop.12':
zr364xx.c:(.text+0xc7d2f): undefined reference to `usb_control_msg'
drivers/built-in.o: In function `pvr2_ctl_timeout':
pvrusb2-hdw.c:(.text+0xcadb6): undefined reference to `usb_unlink_urb'
pvrusb2-hdw.c:(.text+0xcadcb): undefined reference to `usb_unlink_urb'
drivers/built-in.o: In function `pvr2_hdw_create':
(.text+0xcc42c): undefined reference to `usb_alloc_urb'
drivers/built-in.o: In function `pvr2_hdw_create':
(.text+0xcc448): undefined reference to `usb_alloc_urb'
drivers/built-in.o: In function `pvr2_hdw_create':
(.text+0xcc5f9): undefined reference to `usb_set_interface'
drivers/built-in.o: In function `pvr2_hdw_create':
(.text+0xcc65a): undefined reference to `usb_free_urb'
drivers/built-in.o: In function `pvr2_hdw_create':
(.text+0xcc666): undefined reference to `usb_free_urb'
drivers/built-in.o: In function `pvr2_send_request_ex.part.22':
pvrusb2-hdw.c:(.text+0xccbe3): undefined reference to `usb_submit_urb'
pvrusb2-hdw.c:(.text+0xccc83): undefined reference to `usb_submit_urb'
drivers/built-in.o: In function `pvr2_hdw_remove_usb_stuff.part.25':
pvrusb2-hdw.c:(.text+0xcd3f9): undefined reference to `usb_kill_urb'
pvrusb2-hdw.c:(.text+0xcd405): undefined reference to `usb_free_urb'
pvrusb2-hdw.c:(.text+0xcd421): undefined reference to `usb_kill_urb'
pvrusb2-hdw.c:(.text+0xcd42d): undefined reference to `usb_free_urb'
drivers/built-in.o: In function `pvr2_hdw_device_reset':
(.text+0xcd658): undefined reference to `usb_lock_device_for_reset'
drivers/built-in.o: In function `pvr2_hdw_device_reset':
(.text+0xcd664): undefined reference to `usb_reset_device'
drivers/built-in.o: In function `pvr2_hdw_cpureset_assert':
(.text+0xcd6f9): undefined reference to `usb_control_msg'
drivers/built-in.o: In function `pvr2_hdw_cpufw_set_enabled':
(.text+0xcd84e): undefined reference to `usb_control_msg'
drivers/built-in.o: In function `pvr2_upload_firmware1':
pvrusb2-hdw.c:(.text+0xcda47): undefined reference to `usb_clear_halt'
pvrusb2-hdw.c:(.text+0xcdb04): undefined reference to `usb_control_msg'
drivers/built-in.o: In function `pvr2_upload_firmware2':
(.text+0xce7dc): undefined reference to `usb_bulk_msg'
drivers/built-in.o: In function `pvr2_stream_buffer_count':
pvrusb2-io.c:(.text+0xd2e05): undefined reference to `usb_alloc_urb'
pvrusb2-io.c:(.text+0xd2e5b): undefined reference to `usb_kill_urb'
pvrusb2-io.c:(.text+0xd2e9f): undefined reference to `usb_free_urb'
drivers/built-in.o: In function `pvr2_stream_internal_flush':
pvrusb2-io.c:(.text+0xd2f9b): undefined reference to `usb_kill_urb'
drivers/built-in.o: In function `pvr2_buffer_queue':
(.text+0xd3328): undefined reference to `usb_kill_urb'
drivers/built-in.o: In function `pvr2_buffer_queue':
(.text+0xd33ea): undefined reference to `usb_submit_urb'
drivers/built-in.o: In function `stk1160_read_reg':
(.text+0xd3efa): undefined reference to `usb_control_msg'
drivers/built-in.o: In function `stk1160_write_reg':
(.text+0xd3f4f): undefined reference to `usb_control_msg'
drivers/built-in.o: In function `stop_streaming':
stk1160-v4l.c:(.text+0xd4997): undefined reference to `usb_set_interface'
drivers/built-in.o: In function `start_streaming':
stk1160-v4l.c:(.text+0xd4a9f): undefined reference to `usb_set_interface'
stk1160-v4l.c:(.text+0xd4afa): undefined reference to `usb_submit_urb'
stk1160-v4l.c:(.text+0xd4ba3): undefined reference to `usb_set_interface'
drivers/built-in.o: In function `stk1160_isoc_irq':
stk1160-video.c:(.text+0xd509b): undefined reference to `usb_submit_urb'
drivers/built-in.o: In function `stk1160_cancel_isoc':
(.text+0xd50ef): undefined reference to `usb_kill_urb'
drivers/built-in.o: In function `stk1160_free_isoc':
(.text+0xd5155): undefined reference to `usb_free_coherent'
drivers/built-in.o: In function `stk1160_free_isoc':
(.text+0xd515d): undefined reference to `usb_free_urb'
drivers/built-in.o: In function `stk1160_alloc_isoc':
(.text+0xd5278): undefined reference to `usb_alloc_urb'
drivers/built-in.o: In function `stk1160_alloc_isoc':
(.text+0xd52c2): undefined reference to `usb_alloc_coherent'
drivers/built-in.o: In function `stk1160_alloc_isoc':
(.text+0xd53c4): undefined reference to `usb_free_urb'
drivers/built-in.o: In function `zr364xx_driver_init':
zr364xx.c:(.init.text+0x463e): undefined reference to `usb_register_driver'
drivers/built-in.o: In function `pvr_init':
pvrusb2-main.c:(.init.text+0x4662): undefined reference to `usb_register_driver'
drivers/built-in.o: In function `stk1160_usb_driver_init':
stk1160-core.c:(.init.text+0x467d): undefined reference to `usb_register_driver'
drivers/built-in.o: In function `zr364xx_driver_exit':
zr364xx.c:(.exit.text+0x1377): undefined reference to `usb_deregister'
drivers/built-in.o: In function `pvr_exit':
pvrusb2-main.c:(.exit.text+0x1389): undefined reference to `usb_deregister'
drivers/built-in.o: In function `stk1160_usb_driver_exit':
stk1160-core.c:(.exit.text+0x13a0): undefined reference to `usb_deregister'

Suggested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>