Fix calculating io queues number in ENA driver

The maximum number of io_cq was the same number as maximum io_sq
indicated by the device working in normal mode (without LLQ).
It is not always true, especially when LLQ is being enabled.
Fix it.

Submitted by: Michal Krawczyk <mk@semihalf.com>
Reviewed by: byenduri_gmail.com
Obtained from: Semihalf
Sponsored by: Amazon, Inc.
Differential Revision: https://reviews.freebsd.org/D12869