[media] omap3isp: Use a local media device pointer instead

The function has a local variable that points to the media device; use
that instead of finding the media device under the entity.

Signed-off-by: Sakari Ailus <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/platform/omap3isp/ispvideo.c

···
 	int ret;
 
 	mutex_lock(&mdev->graph_mutex);
-	ret = media_graph_walk_init(&graph, entity->graph_obj.mdev);
+	ret = media_graph_walk_init(&graph, mdev);
 	if (ret) {
 		mutex_unlock(&mdev->graph_mutex);
 		return ret;