net: ethernet: fec: remove redundant null check before clk_disable_unprepare()

Because clk_prepare_enable() and clk_disable_unprepare() already checked
NULL clock parameter, so the additional checks are unnecessary, just
remove them.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Acked-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/freescale/fec_main.c

@@ -1960,8 +1960,7 @@ static int fec_enet_clk_enable(struct net_device *ndev, bool enable)
 		mutex_unlock(&fep->ptp_clk_mutex);
 	}
 failed_clk_ptp:
-	if (fep->clk_enet_out)
-		clk_disable_unprepare(fep->clk_enet_out);
+	clk_disable_unprepare(fep->clk_enet_out);
 
 	return ret;
 }