[media] rtl2832_sdr: add support for fc2580 tuner

Add initial support for fc2580 tuner based devices.
Tuner is controlled via V4L2 subdevice API.
Passes v4l2-compliance tests.

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