RDMA/rxe: Enable asynchronous prefetch for ODP MRs

Calling ibv_advise_mr(3) with flags other than IBV_ADVISE_MR_FLAG_FLUSH
invokes an asynchronous request. It is best-effort, and thus can safely be
deferred to the system-wide workqueue.

The reference counter in rxe_mr is used to ensure that the MRs persist and
that rxe is not terminated until the queued work is done.

Signed-off-by: Daisuke Matsuda <dskmtsd@gmail.com>
Link: https://patch.msgid.link/20250522111955.3227-3-dskmtsd@gmail.com


Signed-off-by: Leon Romanovsky <leon@kernel.org>