[media] msi3101: implement stream format 504

That stream format carries 504 x I+Q samples per 1024 USB frame.
Sample resolution is 8-bit signed. Default it when sampling rate
is 9Msps or over.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>