[media] v4l: subdev: Control ioctls support

Pass the control-related ioctls to the subdev driver through the control
framework.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>