[media] media_device: add a topology version field

Every time a graph object is added or removed, the version
of the topology changes. That's a requirement for the new
MEDIA_IOC_G_TOPOLOGY, in order to allow userspace to know
that the topology has changed after a previous call to it.

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/media-entity.c

@@ -173,6 +173,9 @@ void media_gobj_init(struct media_device *mdev,
 		list_add_tail(&gobj->list, &mdev->interfaces);
 		break;
 	}
+
+	mdev->topology_version++;
+
 	dev_dbg_obj(__func__, gobj);
 }
 
@@ -187,6 +190,8 @@ void media_gobj_remove(struct media_gobj *gobj)
 {
 	dev_dbg_obj(__func__, gobj);
 
+	gobj->mdev->topology_version++;
+
 	/* Remove the object from mdev list */
 	list_del(&gobj->list);
 }