[media] media: Move media_device link_notify operation to an ops structure

This will allow adding new operations without increasing the
media_device structure size for drivers that don't implement any media
device operation.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
index 9014362..c68239e 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -808,17 +808,18 @@
 
 	mdev = source->graph_obj.mdev;
 
-	if (mdev->link_notify) {
-		ret = mdev->link_notify(link, flags,
-					MEDIA_DEV_NOTIFY_PRE_LINK_CH);
+	if (mdev->ops && mdev->ops->link_notify) {
+		ret = mdev->ops->link_notify(link, flags,
+					     MEDIA_DEV_NOTIFY_PRE_LINK_CH);
 		if (ret < 0)
 			return ret;
 	}
 
 	ret = __media_entity_setup_link_notify(link, flags);
 
-	if (mdev->link_notify)
-		mdev->link_notify(link, flags, MEDIA_DEV_NOTIFY_POST_LINK_CH);
+	if (mdev->ops && mdev->ops->link_notify)
+		mdev->ops->link_notify(link, flags,
+				       MEDIA_DEV_NOTIFY_POST_LINK_CH);
 
 	return ret;
 }