rtlwifi: Fix scheduling while atomic splat

rtlwifi: Fix scheduling while atomic splat

Following commit cceb0a597320 ("rtlwifi: Add work queue for c2h cmd."),
the following BUG is reported when rtl8723be is used:

BUG: sleeping function called from invalid context at mm/slab.h:432
in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/0
CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W  O    4.11.0-rc3-wl+ #276
Hardware name: TOSHIBA TECRA A50-A/TECRA A50-A, BIOS Version 4.50   09/29/2014
Call Trace:
 <IRQ>
 dump_stack+0x63/0x89
 ___might_sleep+0xe9/0x130
 __might_sleep+0x4a/0x90
 kmem_cache_alloc_trace+0x19f/0x200
 ? rtl_c2hcmd_enqueue+0x3e/0x110 [rtlwifi]
 rtl_c2hcmd_enqueue+0x3e/0x110 [rtlwifi]
 rtl8723be_c2h_packet_handler+0xac/0xc0 [rtl8723be]
 rtl8723be_rx_command_packet+0x37/0x5c [rtl8723be]
 _rtl_pci_rx_interrupt+0x200/0x6b0 [rtl_pci]
 _rtl_pci_interrupt+0x20c/0x5d0 [rtl_pci]
 __handle_irq_event_percpu+0x3f/0x1d0
 handle_irq_event_percpu+0x23/0x60
 handle_irq_event+0x3c/0x60
 handle_fasteoi_irq+0xa2/0x170
 handle_irq+0x20/0x30
 do_IRQ+0x48/0xd0
 common_interrupt+0x89/0x89
...

Although commit cceb0a597320 converted most c2h commands to use a work
queue, the Bluetooth coexistence routines can be in atomic mode when
they execute such a call.

Fixes: cceb0a597320 ("rtlwifi: Add work queue for c2h cmd.")
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>