media: siano: Fix coherent memory allocation failure on arm64

On some architectures such as arm64, siano chip based TV-tuner
USB devices are not recognized correctly due to coherent memory
allocation failure with the following error:

[  663.556135] usbcore: deregistering interface driver smsusb
[  683.624809] smsusb:smsusb_probe: board id=18, interface number 0
[  683.633530] smsusb:smsusb_init_device: smscore_register_device(...) failed, rc -12
[  683.641501] smsusb:smsusb_probe: Device initialized with return code -12
[  683.652978] smsusb: probe of 1-1:1.0 failed with error -12

This is caused by dma_alloc_coherent(NULL, ...) returning NULL in
smscoreapi.c.

To fix this error, allocate the buffer memory for the USB devices
via kmalloc() and let the USB core do the DMA mapping and free.

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>