UBI: error path bugfix

No need to unlock the lock, this will be done at out_unlock.

Signed-off-by: Artem Bityutskiy <[e-mail]>

drivers/mtd/ubi/vmt.c

···
 	/* Reserve physical eraseblocks */
 	if (vol->reserved_pebs > ubi->avail_pebs) {
 		dbg_err("not enough PEBs, only %d available", ubi->avail_pebs);
-		spin_unlock(&ubi->volumes_lock);
 		err = -ENOSPC;
 		goto out_unlock;
 	}