[netdevice] Mark devices as open only if opening succeeds

netdev_close() assumes that devices that are open are on the
open_list, which wasn't true if device specific opening failed.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/netdevice.c

 
 	DBGC ( netdev, "NETDEV %s opening\n", netdev->name );
 
-	/* Mark as opened */
-	netdev->state |= NETDEV_OPEN;
-
 	/* Open the device */
 	if ( ( rc = netdev->op->open ( netdev ) ) != 0 )
 		return rc;
 
+	/* Mark as opened */
+	netdev->state |= NETDEV_OPEN;
+
 	/* Add to head of open devices list */
 	list_add ( &netdev->open_list, &open_net_devices );