backlight: msi-laptop, msi-wmi: fix incomplete registration failure handling

Properly return backlight registration error to parent.
Mark struct backlight_ops as const.
Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Reviewed-by: Anisse Astier <anisse@astier.eu>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

drivers/platform/x86/msi-wmi.c

@@ -138,7 +138,7 @@ static int bl_set_status(struct backlight_device *bd)
 	return msi_wmi_set_block(0, backlight_map[bright]);
 }
 
-static struct backlight_ops msi_backlight_ops = {
+static const struct backlight_ops msi_backlight_ops = {
 	.get_brightness	= bl_get,
 	.update_status	= bl_set_status,
 };
@@ -255,8 +255,10 @@ static int __init msi_wmi_init(void)
 		backlight = backlight_device_register(DRV_NAME, NULL, NULL,
 						      &msi_backlight_ops,
 						      &props);
-		if (IS_ERR(backlight))
+		if (IS_ERR(backlight)) {
+			err = PTR_ERR(backlight);
 			goto err_free_input;
+		}
 
 		err = bl_get(NULL);
 		if (err < 0)