driver model: don't double up() if device registration fails.

I thought this had been fixed some time ago, but must have never been 
picked up..

drivers/base/core.c

@@ -134,7 +134,7 @@ int device_add(struct device *dev)
 	devclass_add_device(dev);
  register_done:
 	if (error) {
-		up(&device_sem);
+		down(&device_sem);
 		list_del_init(&dev->g_list);
 		list_del_init(&dev->node);
 		up(&device_sem);