[media] drxk: Move I2C address into a config structure

Currently, the only parameter to be configured is the I2C
address. However, Terratec H5 logs shows that it needs a different
setting for some things, and it has its own firmware.

So, move the addr into a config structure, in order to allow adding
the required configuration bits.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>