RDMA/irdma: Replace waitqueue and flag with completion

RDMA/irdma: Replace waitqueue and flag with completion

The driver previously used a waitqueue along with an explicit
request_done flag, but without proper barriers around request_done.

An earlier patch by Gui-Dong Han <hanguidong02@gmail.com> attempted
to fix this by adding the missing memory barriers. Rather than
adding the barriers, this patch replaces the waitqueue+flag with
a completion, which is designed for this exact purpose.

Fixes: 44d9e52977a1 ("RDMA/irdma: Implement device initialization definitions")
Fixes: 915cc7ac0f8e ("RDMA/irdma: Add miscellaneous utility definitions")
Link: https://patch.msgid.link/r/20260616155601.1081448-1-jmoroni@google.com
Signed-off-by: Jacob Moroni <jmoroni@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>