net/sched: Retire dsmark qdisc

commit bbe77c14ee6185a61ba6d5e435c1cbb489d2a9ed upstream.

The dsmark qdisc has served us well over the years for diffserv but has not
been getting much attention due to other more popular approaches to do diffserv
services. Most recently it has become a shooting target for 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>