net: fec: Do proper error checking for enet_out clk

An error code returned by devm_clk_get() might have other meanings than
"This clock doesn't exist". So use devm_clk_get_optional() and handle
all remaining errors as fatal.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fec_main.c

@@ -3866,9 +3866,11 @@ fec_probe(struct platform_device *pdev)
 	fep->itr_clk_rate = clk_get_rate(fep->clk_ahb);
 
 	/* enet_out is optional, depends on board */
-	fep->clk_enet_out = devm_clk_get(&pdev->dev, "enet_out");
-	if (IS_ERR(fep->clk_enet_out))
-		fep->clk_enet_out = NULL;
+	fep->clk_enet_out = devm_clk_get_optional(&pdev->dev, "enet_out");
+	if (IS_ERR(fep->clk_enet_out)) {
+		ret = PTR_ERR(fep->clk_enet_out);
+		goto failed_clk;
+	}
 
 	fep->ptp_clk_on = false;
 	mutex_init(&fep->ptp_clk_mutex);