[eoib] Avoid passing a NULL I/O buffer to netdev_tx_complete_err()

Report errors in eoib_duplicate() via netdev_tx_err() rather than
netdev_tx_complete_err(), since netdev_tx_complete_err() accepts only
valid I/O buffers that are currently in the network device's transmit
queue.

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

src/drivers/net/eoib.c

 
  err_post_send:
  err_path:
+	list_del ( &copy->list );
  err_alloc:
-	netdev_tx_complete_err ( netdev, copy, rc );
+	netdev_tx_err ( netdev, copy, rc );
 }
 
 /**