[media] it913x: convert to I2C driver

Change the it913x driver to use the I2C high lever tuner
binding model. As af9035 depends on it, add a code there
to do the binding.

[mchehab@osg.samsung.com: Merge 3 patches into one, because
 we don't want to break bisect due to the conversion]
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>