Add a check for v4l2_dev to v4l2_async_notifier_register() as to fail as
early as possible since this will fail later in v4l2_async_test_notify().
Signed-off-by: NNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>