drm/tegra: dpaux: Fix error handling

The devm_pinctrl_register() function returns an error pointer or a valid
handle. So checking for NULL here is pointless and can never trigger.

Check the returned value with IS_ERR instead and propagate this value as
done in the other functions which call devm_pinctrl_register().

Fixes: 0751bb5c ("drm/tegra: dpaux: Add pinctrl support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dpaux.c

@@ -539,9 +539,9 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	dpaux->desc.owner = THIS_MODULE;
 
 	dpaux->pinctrl = devm_pinctrl_register(&pdev->dev, &dpaux->desc, dpaux);
-	if (!dpaux->pinctrl) {
+	if (IS_ERR(dpaux->pinctrl)) {
 		dev_err(&pdev->dev, "failed to register pincontrol\n");
-		return -ENODEV;
+		return PTR_ERR(dpaux->pinctrl);
 	}
 #endif
 	/* enable and clear all interrupts */