[media] af9035: add support for the tda18218 tuner

Add basic support for the tda18218 tuner and the AVerMedia A835 devices.

Signed-off-by: Gianluca Gennari <gennarone@gmail.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>