backlight: backlight_device_register() return ERR_PTR()

backlight_device_register() returns a valid pointer or ERR_PTR() never
NULL.

Signed-off-by: Dan Carpenter <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Richard Purdie <[e-mail]>

drivers/video/backlight/adx_bl.c

···
 	props.max_brightness = 0xff;
 	bldev = backlight_device_register(dev_name(&pdev->dev), &pdev->dev,
 					  bl, &adx_backlight_ops, &props);
-	if (!bldev) {
-		ret = -ENOMEM;
+	if (IS_ERR(bldev)) {
+		ret = PTR_ERR(bldev);
 		goto out;
 	}