backlight: pm8941-wled: Fix ptr_ret.cocci warnings

drivers/video/backlight/pm8941-wled.c:404:1-3: WARNING: PTR_ERR_OR_ZERO can be used

 Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci
Acked-by: NBjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/video/backlight/pm8941-wled.c

@@ -401,10 +401,7 @@ static int pm8941_wled_probe(struct platform_device *pdev)
 	bl = devm_backlight_device_register(&pdev->dev, wled->name,
 					    &pdev->dev, wled,
 					    &pm8941_wled_ops, &props);
-	if (IS_ERR(bl))
-		return PTR_ERR(bl);
-
-	return 0;
+	return PTR_ERR_OR_ZERO(bl);
 };
 
 static const struct of_device_id pm8941_wled_match_table[] = {