RDMA/bnxt_re: Refactor queue pair creation code

Restructuring the bnxt_re_create_qp function. Listing below the major
changes:
 - Monolithic central part of create_qp where attributes are initialized
   is now enclosed in one function and this new function has few more
   sub-functions.
 - Top level qp limit checking code moved to a function.
 - GSI QP creation and GSI Shadow qp creation code is handled in a sub
   function.

Link: https://lore.kernel.org/r/1581786665-23705-2-git-send-email-devesh.sharma@broadcom.com


Signed-off-by: Naresh Kumar PBS <nareshkumar.pbs@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>