[media] mn88473: finalize driver

Finalize the driver.
It still lacks a lot of features, like all statistics and PLP
filtering, but basic functionality and sensitivity is pretty good
shape.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Reviewed-by: Benjamin Larsson <benjamin@southpole.se>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>