media: i2c: Use the new get_mbus_config pad op

Upstream https://patchwork.linuxtv.org/patch/64669/



Move the existing users of the g_mbus_config video operation to use the
newly introduced get_mbus_config pad operations.

All the ported drivers report a static media bus configuration and do no
support s_mbus_config so the operation implementation has not changed.

Bridge drivers needs to call the new pad operation and will receive an
-ENOICTLCMD when calling the old g_mbus_config video operation

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>