[media] V4L: cosmetic clean up

Improve the use of the WARN_ON() macro and use a local variable, instead
of reduntantly dereferencing a pointer in v4l2-dev.c

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/v4l2-dev.c

@@ -146,10 +146,9 @@ static void v4l2_device_release(struct device *cd)
 	struct v4l2_device *v4l2_dev = vdev->v4l2_dev;
 
 	mutex_lock(&videodev_lock);
-	if (video_device[vdev->minor] != vdev) {
-		mutex_unlock(&videodev_lock);
+	if (WARN_ON(video_device[vdev->minor] != vdev)) {
 		/* should not happen */
-		WARN_ON(1);
+		mutex_unlock(&videodev_lock);
 		return;
 	}
 
@@ -168,7 +167,7 @@ static void v4l2_device_release(struct device *cd)
 	mutex_unlock(&videodev_lock);
 
 #if defined(CONFIG_MEDIA_CONTROLLER)
-	if (vdev->v4l2_dev && vdev->v4l2_dev->mdev &&
+	if (v4l2_dev && v4l2_dev->mdev &&
 	    vdev->vfl_type != VFL_TYPE_SUBDEV)
 		media_device_unregister_entity(&vdev->entity);
 #endif
@@ -556,8 +555,7 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
 	vdev->minor = -1;
 
 	/* the release callback MUST be present */
-	WARN_ON(!vdev->release);
-	if (!vdev->release)
+	if (WARN_ON(!vdev->release))
 		return -EINVAL;
 
 	/* v4l2_fh support */