[media] adv7604/cobalt: missing GPIOLIB dependency

The adv7604 driver depends on GPIOLIB, and therefore cobalt depends
on it as well.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>