RDMA/siw: publish QP after initialization

RDMA/siw: publish QP after initialization

siw_create_qp() currently calls siw_qp_add() before the queues, CQ
pointers, state, completion, and device list entry are ready. A QPN
lookup can therefore reach a QP that is still being constructed.

Move siw_qp_add() to the end of siw_create_qp(), after QP
initialization and before adding the QP to the siw device list.

Fixes: f29dd55b0236 ("rdma/siw: queue pair methods")
Link: https://patch.msgid.link/r/20260630060040.966461-1-ruoyuw560@gmail.com
Suggested-by: Bernard Metzler <bernard.metzler@linux.dev>
Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>
Acked-by: Bernard Metzler <bernard.metzler@linux.dev>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>