UBI: minor serialization fix

The @vol->upd_marker should be protected by the @ubi->device_mutex,
otherwise 'paranoid_check_volume()' complains sometimes because
vol->upd_marker is 1 while vtbl_rec->upd_marker is 0.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/upd.c

@@ -70,8 +70,8 @@ static int set_update_marker(struct ubi_device *ubi, struct ubi_volume *vol)
 
 	mutex_lock(&ubi->device_mutex);
 	err = ubi_change_vtbl_record(ubi, vol->vol_id, &vtbl_rec);
-	mutex_unlock(&ubi->device_mutex);
 	vol->upd_marker = 1;
+	mutex_unlock(&ubi->device_mutex);
 	return err;
 }
 
@@ -111,8 +111,8 @@ static int clear_update_marker(struct ubi_device *ubi, struct ubi_volume *vol,
 
 	mutex_lock(&ubi->device_mutex);
 	err = ubi_change_vtbl_record(ubi, vol->vol_id, &vtbl_rec);
-	mutex_unlock(&ubi->device_mutex);
 	vol->upd_marker = 0;
+	mutex_unlock(&ubi->device_mutex);
 	return err;
 }