[media] radio-mr800: move clamp_t check inside amradio_set_freq()

[media] radio-mr800: move clamp_t check inside amradio_set_freq()

If i run verbose v4l2-compliance with my radio-mr800 device few times
then i get warning about frequency out of range:

root@machine:~# v4l2-compliance -r /dev/radio0 -v 2
is radio
Driver Info:
	Driver name   : radio-mr800
	Card type     : AverMedia MR 800 USB FM Radio
	Bus info      : usb-0000:00:1a.0-1.2
	Driver version: 3.9.0
	Capabilities  : 0x80050400
		Tuner
		Radio
		Device Capabilities
	Device Caps   : 0x00050400
		Tuner
		Radio
Compliance test for device /dev/radio0 (not using libv4l2):
Required ioctls:
	test VIDIOC_QUERYCAP: OK
Allow for multiple opens:
	test second radio open: OK
	test VIDIOC_QUERYCAP: OK
	test VIDIOC_G/S_PRIORITY: OK
Debug ioctls:
	test VIDIOC_DBG_G_CHIP_IDENT: OK (Not Supported)
	test VIDIOC_DBG_G/S_REGISTER: OK (Not Supported)
	test VIDIOC_LOG_STATUS: OK
Input ioctls:
	test VIDIOC_G/S_TUNER: OK
		warn: v4l2-test-input-output.cpp(234): returned tuner 0 frequency out
of range (6550200 not in [1400000...1728000])
	test VIDIOC_G/S_FREQUENCY: OK
	test VIDIOC_S_HW_FREQ_SEEK: OK
	test VIDIOC_ENUMAUDIO: OK (Not Supported)
	test VIDIOC_G/S/ENUMINPUT: OK (Not Supported)
	test VIDIOC_G/S_AUDIO: OK (Not Supported)
	Inputs: 0 Audio Inputs: 0 Tuners: 1
Output ioctls:
	test VIDIOC_G/S_MODULATOR: OK (Not Supported)
	test VIDIOC_G/S_FREQUENCY: OK
	test VIDIOC_ENUMAUDOUT: OK (Not Supported)
	test VIDIOC_G/S/ENUMOUTPUT: OK (Not Supported)
	test VIDIOC_G/S_AUDOUT: OK (Not Supported)
	Outputs: 0 Audio Outputs: 0 Modulators: 0
Control ioctls:
		info: checking v4l2_queryctrl of control 'User Controls' (0x00980001)
		info: checking v4l2_queryctrl of control 'Mute' (0x00980909)
		info: checking v4l2_queryctrl of control 'Mute' (0x00980909)
	test VIDIOC_QUERYCTRL/MENU: OK
		info: checking control 'User Controls' (0x00980001)
		info: checking control 'Mute' (0x00980909)
	test VIDIOC_G/S_CTRL: OK
		info: checking extended control 'User Controls' (0x00980001)
		info: checking extended control 'Mute' (0x00980909)
	test VIDIOC_G/S/TRY_EXT_CTRLS: OK
		info: checking control event 'User Controls' (0x00980001)
		info: checking control event 'Mute' (0x00980909)
	test VIDIOC_(UN)SUBSCRIBE_EVENT/DQEVENT: OK
	test VIDIOC_G/S_JPEGCOMP: OK (Not Supported)
	Standard Controls: 2 Private Controls: 0
Input/Output configuration ioctls:
	test VIDIOC_ENUM/G/S/QUERY_STD: OK (Not Supported)
	test VIDIOC_ENUM/G/S/QUERY_DV_PRESETS: OK (Not Supported)
	test VIDIOC_ENUM/G/S/QUERY_DV_TIMINGS: OK (Not Supported)
	test VIDIOC_DV_TIMINGS_CAP: OK (Not Supported)
Format ioctls:
	test VIDIOC_ENUM_FMT/FRAMESIZES/FRAMEINTERVALS: OK (Not Supported)
	test VIDIOC_G/S_PARM: OK (Not Supported)
	test VIDIOC_G_FBUF: OK (Not Supported)
	test VIDIOC_G_FMT: OK (Not Supported)
	test VIDIOC_TRY_FMT: OK (Not Supported)
	test VIDIOC_S_FMT: OK (Not Supported)
	test VIDIOC_G_SLICED_VBI_CAP: OK (Not Supported)
Codec ioctls:
	test VIDIOC_(TRY_)ENCODER_CMD: OK (Not Supported)
	test VIDIOC_G_ENC_INDEX: OK (Not Supported)
	test VIDIOC_(TRY_)DECODER_CMD: OK (Not Supported)
Buffer ioctls:
	test VIDIOC_REQBUFS/CREATE_BUFS/QUERYBUF: OK (Not Supported)
Total: 38, Succeeded: 38, Failed: 0, Warnings: 1

Some printk() debugging showed that vidioc_s_hw_freq_seek() setups
radio->curfreq to out of range value (lines 395-396) and calls
amradio_set_freq() to set this frequency on device without any
out-of-range checks.

Patch protects from setting up frequency on device to incorrect value
moving clamp_t check inside amradio_set_freq. With this patch we can
call amradio_set_freq() with out of range frequency from any place.
Also put comment that sometimes radio->curfreq is set to out of range
value in vidioc_s_hw_freq_seek().

Signed-off-by: Alexey Klimov <klimov.linux@gmail.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>