thunderbolt: Unlock on error path in tb_domain_add()

We accidentally deleted this unlock on the error path.  Undelete it.

Fixes: 7f0a34d7 ("thunderbolt: Decrease control channel timeout for software connection manager")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/domain.c

@@ -493,6 +493,7 @@ int tb_domain_add(struct tb *tb)
 	device_del(&tb->dev);
 err_ctl_stop:
 	tb_ctl_stop(tb->ctl);
+	mutex_unlock(&tb->lock);
 
 	return ret;
 }