phy: fix return value check in armada375_usb_phy_probe()

In case of error, the function devm_ioremap_resource() returns
ERR_PTR() and never returns NULL. The NULL test in the return
value check should be replaced with IS_ERR().
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/phy/phy-armada375-usb2.c

@@ -118,8 +118,8 @@ static int armada375_usb_phy_probe(struct platform_device *pdev)
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	usb_cluster_base = devm_ioremap_resource(&pdev->dev, res);
-	if (!usb_cluster_base)
-		return -ENOMEM;
+	if (IS_ERR(usb_cluster_base))
+		return PTR_ERR(usb_cluster_base);
 
 	phy = devm_phy_create(dev, NULL, &armada375_usb_phy_ops);
 	if (IS_ERR(phy)) {