backlight: max8925_bl: Fix error handling path

Properly unregister a previously registered backlight device object in error
handling of max8925_backlight_probe.
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

drivers/video/backlight/max8925_bl.c

@@ -162,6 +162,7 @@ static int __devinit max8925_backlight_probe(struct platform_device *pdev)
 	backlight_update_status(bl);
 	return 0;
 out:
+	backlight_device_unregister(bl);
 	kfree(data);
 	return ret;
 }