qed: Encapsulate interrupt counters in struct

We already have an API struct that contains interrupt-related
numbers. Use it to encapsulate all information relating to the
status of SBs as (used|free).

Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>