tc: cake: add cake_mq support

This adds support for the cake_mq variant of sch_cake to tc.

Signed-off-by: Jonas Köppeler <j.koeppeler@tu-berlin.de>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: David Ahern <dsahern@kernel.org>