When deleting the last child the level of a class should drop to zero.
Noticed by Andreas Mueller <andreas@stapelspeicher.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
        do {
                level = 0;
                list_for_each_entry(p, &cl->children, siblings) {
-                       if (p->level > level)
-                               level = p->level;
+                       if (p->level >= level)
+                               level = p->level + 1;
                }
-               cl->level = level + 1;
+               cl->level = level;
        } while ((cl = cl->cl_parent) != NULL);
 }