nfp: abm: track all offload-enabled qdiscs

Allocate an object corresponding to any offloaded qdisc we are
informed about by the kernel.  Not only the qdiscs we have a
chance of offloading.

The count of created objects will be used to decide whether
the ethtool TC offload can be disabled, since otherwise we may
miss destroy commands.

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>