[media] uvcvideo: Properly report the inactive flag for inactive controls

Note the unused in this patch slave_ids addition to the mappings will get
used in a follow up patch to generate control change events for the slave
ctrls when their flags change due to the master control changing value.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>