nfp: abm: restructure Qdisc handling

In preparation of handling more Qdisc types switch to a different
offload strategy.  We have now recreated the Qdisc hierarchy in
the driver.  Every time the hierarchy changes parse it, and update
the configuration of the HW accordingly.

While at it drop the support of pretending that we can instantiate
a single queue on a multi-queue device in HW/FW.  MQ is now required,
and each queue will have its own instance of RED.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>