io_uring: remove io_req_complete_post_tw

It's only used in one place. Inline it.

Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20221125103412.1425305-2-dylany@meta.com


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