net/sched: Retire tcindex classifier

The tcindex classifier has served us well for about a quarter of a century
but has not been getting much TLC due to lack of known users. Most recently
it has become easy prey to syzkaller. For this reason, we are retiring it.

Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>