ntb_netdev: remove from list on exit

The ntb_netdev device is not removed from the global list of devices
upon device removal. If the device is re-added, the removal code would
find the first instance and try to remove an already removed device.

Signed-off-by: Jon Mason <[e-mail]>

drivers/net/ntb_netdev.c

···
 	if (dev == NULL)
 		return;
 
+	list_del(&dev->list);
+
 	ndev = dev->ndev;
 
 	unregister_netdev(ndev);