v4l2-event: v4l2_event_queue: do nothing if vdev == NULL

v4l2-event: v4l2_event_queue: do nothing if vdev == NULL

If the vdev pointer == NULL, then just return.

This makes it easier for subdev drivers to use this function without having to
check if the sd->devnode pointer is NULL or not.

Bug 1770474

Change-Id: I4d9798b58ea13e987dcf50442a96694a8f803291
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Ken Chang <kenc@nvidia.com>
Reviewed-on: http://git-master/r/1154256
(cherry picked from commit 4e09f1b068c7f67926258f6b0a802fe5691ccd4b)
Signed-off-by: Ahung Cheng <ahcheng@nvidia.com>
Reviewed-on: http://git-master/r/1165707
Reviewed-by: Hayden Du <haydend@nvidia.com>