pinctrl: vt8500: wmt: Fix checking return value of pinctrl_register()

pinctrl_register() returns NULL on error.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Tony Prisk <linux@prisktech.co.nz>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>

drivers/pinctrl/vt8500/pinctrl-wmt.c

@@ -588,7 +588,7 @@ int wmt_pinctrl_probe(struct platform_device *pdev,
 	data->dev = &pdev->dev;
 
 	data->pctl_dev = pinctrl_register(&wmt_desc, &pdev->dev, data);
-	if (IS_ERR(data->pctl_dev)) {
+	if (!data->pctl_dev) {
 		dev_err(&pdev->dev, "Failed to register pinctrl\n");
 		return -EINVAL;
 	}