io_uring: open code __io_post_aux_cqe()

There is no reason to keep __io_post_aux_cqe() separately from
io_post_aux_cqe().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2c4c1f68d694deea25a212fc09bbb11f330cd82e.1742829388.git.asml.silence@gmail.com


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