media: rcar-vin: Do not hold the group lock when unregistering notifier

There is no need to hold the group lock when unregistering the notifier,
but doing so triggers a warning about a possible cyclic lock dependency.

The lock warning cover the case where a subdevice is about to be bound
to the notifier at the same time as it's unregistered. The locking for
this scenario is handled in the v4l2-async framework so it's safe to
remove the lock in the driver. This match the locking logic in the
driver for when the notifier in question is registered.
Signed-off-by: NNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: NHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/platform/rcar-vin/rcar-core.c

@@ -349,12 +349,10 @@ static int rvin_group_parse_of(struct rvin_dev *vin, unsigned int port,
 
 static void rvin_group_notifier_cleanup(struct rvin_dev *vin)
 {
-	mutex_lock(&vin->group->lock);
 	if (&vin->v4l2_dev == vin->group->notifier.v4l2_dev) {
 		v4l2_async_nf_unregister(&vin->group->notifier);
 		v4l2_async_nf_cleanup(&vin->group->notifier);
 	}
-	mutex_unlock(&vin->group->lock);
 }
 
 static int rvin_group_notifier_init(struct rvin_dev *vin, unsigned int port,