net: bcmgenet: Avoid touching non-existent interrupt

As platform_get_irq() now prints an error when the interrupt does not
exist, we are getting a confusing error message in case the optional
WOL IRQ is not defined:

  bcmgenet fd58000.ethernet: IRQ index 2 not found

Fix this by using the platform_get_irq_optional().
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/genet/bcmgenet.c

@@ -3459,7 +3459,7 @@ static int bcmgenet_probe(struct platform_device *pdev)
 	priv = netdev_priv(dev);
 	priv->irq0 = platform_get_irq(pdev, 0);
 	priv->irq1 = platform_get_irq(pdev, 1);
-	priv->wol_irq = platform_get_irq(pdev, 2);
+	priv->wol_irq = platform_get_irq_optional(pdev, 2);
 	if (!priv->irq0 || !priv->irq1) {
 		dev_err(&pdev->dev, "can't find IRQs\n");
 		err = -EINVAL;