sif: Add vendor flag to support testing without oversized CQs

sif: Add vendor flag to support testing without oversized CQs

After introduction of extra CQ entries to reduce risk of
having duplicate completions overflow a CQ, we no longer can
trigger various CQ overflow scenarios without running a lot of
requests. We need to be able to test with a minimal set of operations
to allow co-sim based tests for further analysis.

Introduce a new vendor_flag no_x_cqe = 0x80 to turn off
the allocation of extra CQEs.

Orabug: 24919301

Signed-off-by: Knut Omang <knut.omang@oracle.com>
Reviewed-by: Francisco Triviño <francisco.trivino@oracle.com>