ionic: remove the cq_info to save more memory

With a little simple math we don't need another struct array to
find the completion structs, so we can remove the ionic_cq_info
altogether.  This doesn't really save anything in the ionic_cq
since it gets padded out to the cacheline, but it does remove
the parallel array allocation of 8 * num_descriptors, or about
8 Kbytes per queue in a default configuration.

Suggested-by: Neel Patel <npatel2@amd.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>