The check whether an async sub-device is bound to a notifier was performed
without list_lock held, making it possible for another process to
unbind the async sub-device before the sub-device unregistration function
proceeds to take the lock.
Fix this by first acquiring the lock and then proceeding with the check.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Acked-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>