RDMA/bnxt_re: Refactor notification queue management code

RDMA/bnxt_re: Refactor notification queue management code

Cleaning up the notification queue data structures and management
code. The CQ and SRQ event handlers have been type defined instead of
in-place declaration. NQ doorbell register descriptor has been added in
base NQ structure.  The nq->vector has been renamed to nq->msix_vec.

Link: https://lore.kernel.org/r/1581786665-23705-7-git-send-email-devesh.sharma@broadcom.com
Signed-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>