RDMA/uverbs: Use UMEM attributes for QP creation

RDMA/uverbs: Use UMEM attributes for QP creation

Apply the per-attribute UMEM model to the QP create method. Add
three optional UMEM attributes that drivers pick from based on
how their user ABI lays out the QP rings:

- CREATE_QP_BUF_UMEM is a single user buffer that backs both
  the SQ and RQ of one QP. This is the common case where
  userspace pins one contiguous WQE region for the QP.
- CREATE_QP_SQ_BUF_UMEM and CREATE_QP_RQ_BUF_UMEM are a pair
  of user buffers backing the SQ and RQ independently, used
  when the two rings live in physically distinct user
  allocations and must be pinned and addressed separately.

Existing drivers would map their current umems as follows:

- mlx5: BUF for normal QPs (one ucmd->buf_addr covers SQ+RQ);
  for IB_QPT_RAW_PACKET and IB_QP_CREATE_SOURCE_QPN, the RQ
  side comes from ucmd->buf_addr (RQ-sized) via RQ_BUF and
  the SQ from ucmd->sq_buf_addr via SQ_BUF.
- mlx4: BUF, single ucmd.buf_addr covering SQ+RQ.
- hns: BUF, single ucmd.buf_addr covering SQ + ext-SGE + RQ.
- erdma: BUF, single ureq.qbuf_va sliced by the kernel into
  SQ at offset 0 and RQ at rq_offset.
- bnxt_re: SQ_BUF (ureq->qpsva) + RQ_BUF (ureq->qprva, the
  RQ side is skipped when the QP uses an SRQ).
- vmw_pvrdma: SQ_BUF (sbuf_addr) + RQ_BUF (rbuf_addr, the RQ
  side is skipped when the QP uses an SRQ).
- qedr: SQ_BUF (sq_addr) + RQ_BUF (rq_addr) for whichever
  side the QP type actually has (no SQ for XRC_TGT/GSI; no
  RQ for XRC_INI/XRC_TGT/SRQ).
- ionic: SQ_BUF (req.sq.addr) + RQ_BUF (req.rq.addr); both
  are skipped when the rings are placed in CMB instead of
  host memory.
- mana: raw-packet QP uses SQ_BUF (sq_buf_addr) only; the RC
  path uses multiple per-queue user buffers (ucmd.queue_buf[])
  that do not fit the SQ/RQ pair semantics of these attrs and
  stays on the legacy UHW path.
- efa, irdma, hfi1, ocrdma, mthca, cxgb4 and usnic do not pin
  a QP WQE buffer via umem; none of these attributes apply.

Link: https://patch.msgid.link/r/20260529134312.2836341-13-jiri@resnulli.us
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>