RDMA/bnxt_re: Simplify obtaining queue entry from hw ring

Restructring the data path and control path queue management code to
simplify the way a queue element is extracted from the hardware ring.

Introduced a new function which will give a pointer to the next ring item
depending upon the current cons/prod index in the hardware queue.

Further, there are hardcoding when size of queue entry is calculated,
replacing it with an inline function. This function would be easier to
expand if need going forward.

The code section to initialize the PSN search areas has also been
restructured and couple of functions has been added there.

Link: https://lore.kernel.org/r/1585851136-2316-4-git-send-email-devesh.sharma@broadcom.com


Signed-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>