nfp: abm: rename qdiscs -> red_qdiscs

Rename qdiscs member to red_qdiscs.  One of following patches will
use the name qdiscs for tracking all qdisc types.

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>