RDMA/bnxt_re: Refactor bnxt_re_create_cq()

RDMA/bnxt_re: Refactor bnxt_re_create_cq()

Some applications may allocate dmabuf based memory for CQs. To support
this, update the existing code to use SZ_4K to specify supported HW
page size for CQs, as we support only 4K pages for now.
Call ib_umem_find_best_pgsz() to ensure umem supports this requested
page size. A helper function includes these changes.

Link: https://patch.msgid.link/r/20260302110036.36387-5-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>