Merge branch 'net-sched-teql-enforce-hierarchy-placement'

Jamal Hadi Salim says:

====================
net/sched: teql: Enforce hierarchy placement

GangMin Kim <km.kim1503@gmail.com> managed to create a UAF on qfq by inserting
teql as a child qdisc and exploiting a qlen sync issue.
teql is not intended to be used as a child qdisc. Lets enforce that rule in
patch #1. Although patch #1 fixes the issue, we prevent another potential qlen
exploit in qfq in patch #2 by enforcing the child's active status is not
determined by inspecting the qlen. In patch #3 we add a tdc test case.
====================

Link: https://patch.msgid.link/20260114160243.913069-1-jhs@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>