[media] cx23885: add I2C client for CI into state and handle unregistering

If the CI chip has an I2C driver, we need to store I2C client into state.

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