RDMA/siw: Always report immediate post SQ errors

RDMA/siw: Always report immediate post SQ errors

In siw_post_send(), any immediate error encountered during processing of
the work request list must be reported to the caller, even if previous
work requests in that list were just accepted and added to the send queue.

Not reporting those errors confuses the caller, which would wait
indefinitely for the failing and potentially subsequently aborted work
requests completion.

This fixes a case where immediate errors were overwritten by subsequent
code in siw_post_send().

Fixes: 303ae1cdfdf7 ("rdma/siw: application interface")
Link: https://patch.msgid.link/r/20250923144536.103825-1-bernard.metzler@linux.dev
Suggested-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Bernard Metzler <bernard.metzler@linux.dev>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>