net/sched: Retire rsvp classifier

The rsvp classifier has served us well for about a quarter of a century but has
has not been getting much maintenance attention due to lack of known users.

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