io_uring/net: canonise accept mshot handling

Use a more recognisable pattern for mshot accept, first try to post an
mshot cqe if needed and after do terminating handling.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/daf5c0df7e2966deb0a115021c065fc6161a52d7.1740331076.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>