RDMA/bnxt_re: Code refactor while populating user MRs

Refactor code that populates MR page buffer list. Instead of allocating a
pbl_tbl to hold the buffer list, pass the struct ib_umem directly to
bnxt_qplib_alloc_init_hwq() as done for other user space memories.  Fix
the PBL level to handle the above mentioned change.

Also, remove an unwanted flag from the input to bnxt_qplib_reg_mr()
function.

Link: https://lore.kernel.org/r/1610012608-14528-2-git-send-email-selvin.xavier@broadcom.com
Signed-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>