backlight: 88pm860x_bl: fix error handling in pm860x_backlight_probe

This patch properly unregisters a previously registered backlight device object
in error handling

Signed-off-by: Axel Lin <[e-mail]>
Signed-off-by: Richard Purdie <[e-mail]>

drivers/video/backlight/88pm860x_bl.c

···
 	backlight_update_status(bl);
 	return 0;
 out:
+	backlight_device_unregister(bl);
 	kfree(data);
 	return ret;
 }