net: fec: handle optional clk_ptp more gracefully

When the optional clk_ptp is absent, we can just set it to NULL, and
clk API will just handle it gracefully.  It saves us from checking
clk_ptp whenever calling into clk API.

Also since clk_ptp is optional, the "ret" variable shouldn't be set
in case that the clock is absent.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fec.c

@@ -1806,13 +1806,12 @@ fec_probe(struct platform_device *pdev)
 	fep->bufdesc_ex =
 		pdev->id_entry->driver_data & FEC_QUIRK_HAS_BUFDESC_EX;
 	if (IS_ERR(fep->clk_ptp)) {
-		ret = PTR_ERR(fep->clk_ptp);
+		fep->clk_ptp = NULL;
 		fep->bufdesc_ex = 0;
 	}
 
 	clk_prepare_enable(fep->clk_ahb);
 	clk_prepare_enable(fep->clk_ipg);
-	if (!IS_ERR(fep->clk_ptp))
 	clk_prepare_enable(fep->clk_ptp);
 
 	reg_phy = devm_regulator_get(&pdev->dev, "phy");
@@ -1878,7 +1877,6 @@ fec_probe(struct platform_device *pdev)
 failed_regulator:
 	clk_disable_unprepare(fep->clk_ahb);
 	clk_disable_unprepare(fep->clk_ipg);
-	if (!IS_ERR(fep->clk_ptp))
 	clk_disable_unprepare(fep->clk_ptp);
 failed_pin:
 failed_clk: