ubi_sync_erase
ret = ubi_sync_erase(ubi, old_fm->e[i], 0);
ret = ubi_sync_erase(ubi, old_fm->e[0], 0);
int ubi_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e, int torture);
err = ubi_sync_erase(ubi, e, wl_wrk->torture);
err = ubi_sync_erase(ubi, e, false);