[media] cx231xx: use own i2c_client for eeprom access

This is a preparation for deleting the otherwise useless i2c_clients
that are allocated for all the i2c master adapters.

Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>