[media] media: remove media entity .parent field

Now that the struct media_entity .parent field is unused, it can be
safely removed. Since all the previous users were converted to use
the .mdev field from the embedded struct media_gobj instead.
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

include/media/media-entity.h

@@ -103,7 +103,6 @@ struct media_entity_operations {
 struct media_entity {
 	struct media_gobj graph_obj;
 	struct list_head list;
-	struct media_device *parent;	/* Media device this entity belongs to*/
 	const char *name;		/* Entity name */
 	u32 type;			/* Entity type (MEDIA_ENT_T_*) */
 	u32 revision;			/* Entity revision, driver specific */