upnp: items are already sorted

Since items are already sorted by the server.

modules/services_discovery/upnp.cpp

@@ -839,6 +839,7 @@ static int Open( vlc_object_t *p_this )
     }
 
     p_access->pf_readdir = ReadDirectory;
+    p_access->info.b_dir_sorted = true;
 
     return VLC_SUCCESS;
 }