[media] media/v4l2-ctrls: Add execute flags to write_only controls

Any control that sets FLAG_WRITE_ONLY should OR it with
FLAG_EXECUTE_ON_WRITE.

So we can keep the current meaning of WRITE_ONLY.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>