[media] rtl28xxu: switch rtl2832 demod attach to I2C binding

As rtl2832 driver support now I2C binding we will switch to that one.

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