net: lapbether: Close the LAPB device before its underlying Ethernet device closes

When a virtual LAPB device's underlying Ethernet device closes, the LAPB
device is also closed.

However, currently the LAPB device is closed after the Ethernet device
closes. It would be better to close it before the Ethernet device closes.
This would allow the LAPB device to transmit a last frame to notify the
other side that it is disconnecting.
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/lapbether.c

@@ -421,8 +421,8 @@ static int lapbeth_device_event(struct notifier_block *this,
 		if (lapbeth_get_x25_dev(dev) == NULL)
 			lapbeth_new_device(dev);
 		break;
-	case NETDEV_DOWN:	
-		/* ethernet device closed -> close LAPB interface */
+	case NETDEV_GOING_DOWN:
+		/* ethernet device closes -> close LAPB interface */
 		lapbeth = lapbeth_get_x25_dev(dev);
 		if (lapbeth) 
 			dev_close(lapbeth->axdev);