qed: Remove assumption on SB order in IGU

Current code assumes there's a known layout for SBs in the IGU,
where all the SBs of a single entity would be laid in consecutive
order of vectors.

While the assumption is still kept by management firmware, we already
have the necessary information to eliminate it, so no reason to keep
it in code.

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