[media] media-device: supress backlinks at G_TOPOLOGY ioctl

Due to the graph traversal algorithm currently in usage, we
need a copy of all data links. Those backlinks should not be
send to userspace, as otherwise, all links there will be
duplicated.

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index fd19aec..3b591d7 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -96,6 +96,7 @@
  * @reverse:	Pointer to the link for the reverse direction of a pad to pad
  *		link.
  * @flags:	Link flags, as defined in uapi/media.h (MEDIA_LNK_FL_*)
+ * @is_backlink: Indicate if the link is a backlink.
  */
 struct media_link {
 	struct media_gobj graph_obj;
@@ -112,6 +113,7 @@
 	};
 	struct media_link *reverse;
 	unsigned long flags;
+	bool is_backlink;
 };
 
 /**