net: xilinx: 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>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/xilinx/xilinx_axienet_main.c

@@ -2038,8 +2038,7 @@ static int axienet_remove(struct platform_device *pdev)
 
 	axienet_mdio_teardown(lp);
 
-	if (lp->clk)
-		clk_disable_unprepare(lp->clk);
+	clk_disable_unprepare(lp->clk);
 
 	of_node_put(lp->phy_node);
 	lp->phy_node = NULL;