CVE-2026-72494: RDMA/irdma: Replace waitqueue and flag with completion

In the Linux kernel, the following vulnerability has been resolved:

RDMA/irdma: Replace waitqueue and flag with completion

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

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.