[media] v4l: vsp1: Fix routing cleanup when stopping the stream

Commit d9b45ed3 ("v4l: vsp1: Support
multi-input entities") reworked pipeline routing configuration and
introduced a bug by writing to the entities routing registers without
first checking whether the entity had a routing register. This results
in overwriting the value at offset 0 of the device register space when
stopping the stream.

Fix this by skipping routing register write for entities without a
routing register.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/platform/vsp1/vsp1_video.c

@@ -479,7 +479,7 @@ static int vsp1_pipeline_stop(struct vsp1_pipeline *pipe)
 	ret = ret == 0 ? -ETIMEDOUT : 0;
 
 	list_for_each_entry(entity, &pipe->entities, list_pipe) {
-		if (entity->route)
+		if (entity->route && entity->route->reg)
 			vsp1_write(entity->vsp1, entity->route->reg,
 				   VI6_DPR_NODE_UNUSED);