pinctrl: artpec6: Fix return value check in artpec6_pmx_probe()

In case of error, the function pinctrl_register() returns
ERR_PTR() not NULL. The NULL test in the return value check
should be replaced with IS_ERR().

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-artpec6.c

@@ -937,9 +937,9 @@ static int artpec6_pmx_probe(struct platform_device *pdev)
 	pmx->num_pin_groups = ARRAY_SIZE(artpec6_pin_groups);
 	pmx->pctl	    = pinctrl_register(&artpec6_desc, &pdev->dev, pmx);
 
-	if (!pmx->pctl) {
+	if (IS_ERR(pmx->pctl)) {
 		dev_err(&pdev->dev, "could not register pinctrl driver\n");
-		return -EINVAL;
+		return PTR_ERR(pmx->pctl);
 	}
 
 	platform_set_drvdata(pdev, pmx);