pinctrl: ns2: fix return value check in ns2_pinmux_probe()

In case of error, the function pinctrl_register() returns
NULL not ERR_PTR(). The IS_ERR() test in the return value
check should be replaced with NULL test.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/bcm/pinctrl-ns2-mux.c

@@ -1089,9 +1089,9 @@ static int ns2_pinmux_probe(struct platform_device *pdev)
 
 	pinctrl->pctl = pinctrl_register(&ns2_pinctrl_desc, &pdev->dev,
 			pinctrl);
-	if (!pinctrl->pctl) {
+	if (IS_ERR(pinctrl->pctl)) {
 		dev_err(&pdev->dev, "unable to register IOMUX pinctrl\n");
-		return -EINVAL;
+		return PTR_ERR(pinctrl->pctl);
 	}
 
 	return 0;