tc.c doesn't build against current kernel headers.

[Rob Landley]

A defconfig musl build against a toolchain using linux-6.10 headers goes:

networking/tc.c: In function 'cbq_print_opt':
networking/tc.c:236:27: error: 'TCA_CBQ_MAX' undeclared (first use in 
this function); did you mean 'TCA_CBS_MAX'?
   236 |         struct rtattr *tb[TCA_CBQ_MAX+1];

Because:

commit 33241dca486264193ed68167c8eeae1fb197f3df
Author: Jamal Hadi Salim <jhs at mojatatu.com>
Date:   Sat Dec 23 09:01:54 2023 -0500

net/sched: Remove uapi support for CBQ qdisc

Commit 051d44209842 ("net/sched: Retire CBQ qdisc") retired the CBQ 
qdisc. Remove UAPI for it. Iproute2 will sync by equally removing it 
from user space.

Rob