net: fec_main: Use platform_get_irq_byname_optional() to avoid error message

Failed to get irq using name is NOT fatal as driver will use index
to get irq instead, use platform_get_irq_byname_optional() instead
of platform_get_irq_byname() to avoid below error message during
probe:

[    0.819312] fec 30be0000.ethernet: IRQ int0 not found
[    0.824433] fec 30be0000.ethernet: IRQ int1 not found
[    0.829539] fec 30be0000.ethernet: IRQ int2 not found
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Fugang Duan <fugang.duan@nxp.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fec_main.c

@@ -3558,7 +3558,7 @@ fec_probe(struct platform_device *pdev)
 
 	for (i = 0; i < irq_cnt; i++) {
 		snprintf(irq_name, sizeof(irq_name), "int%d", i);
-		irq = platform_get_irq_byname(pdev, irq_name);
+		irq = platform_get_irq_byname_optional(pdev, irq_name);
 		if (irq < 0)
 			irq = platform_get_irq(pdev, i);
 		if (irq < 0) {