[media] v4l2-ioctl: handle priority handling based on a table lookup

Rather than checking the priority for each ioctl that needs to, just mark
such ioctls in the table and do it only once.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>