net: stmmac: use netif_set_real_num_{rx,tx}_queues

In the submission of the lastest multiple buffer patch set, this fix was lost.
I am sending this patch to put it right again. The fix was originally proposed
by Arnd Bergmann.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Joao Pinto <jpinto@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -4103,8 +4103,8 @@ int stmmac_dvr_probe(struct device *device,
 		goto error_hw_init;
 
 	/* Configure real RX and TX queues */
-	ndev->real_num_rx_queues = priv->plat->rx_queues_to_use;
-	ndev->real_num_tx_queues = priv->plat->tx_queues_to_use;
+	netif_set_real_num_rx_queues(ndev, priv->plat->rx_queues_to_use);
+	netif_set_real_num_tx_queues(ndev, priv->plat->tx_queues_to_use);
 
 	ndev->netdev_ops = &stmmac_netdev_ops;