V4L/DVB: v4l2-dev: remove unnecessary lock around atomic clear_bit

No need to lock when unregistering the device: clear_bit is already an
atomic operation.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 65a7b30..0ca7ec9 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/drivers/media/video/v4l2-dev.c
@@ -600,9 +600,7 @@
 	if (!vdev || !video_is_registered(vdev))
 		return;
 
-	mutex_lock(&videodev_lock);
 	clear_bit(V4L2_FL_REGISTERED, &vdev->flags);
-	mutex_unlock(&videodev_lock);
 	device_unregister(&vdev->dev);
 }
 EXPORT_SYMBOL(video_unregister_device);