RDMA/bnxt_re: Refactor bnxt_re_init_user_qp()

RDMA/bnxt_re: Refactor bnxt_re_init_user_qp()

The umem changes for CQ added a helper - bnxt_re_setup_sginfo().
Use the same helper for QP creation since we support only 4K
pages for QP ring memory too.

Add a new helper function bnxt_re_get_psn_bytes() to improve
readability as this code will be updated in subsequent patches.

Link: https://patch.msgid.link/r/20260519150041.7251-2-sriharsha.basavapatna@broadcom.com
Signed-off-by: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Reviewed-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>