io_uring: inline io_queue_sqe()

Inline io_queue_sqe() as there is only one caller left, and rename
__io_queue_sqe().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d5742683b7a7caceb1c054e91e5b9135b0f3b858.1650056133.git.asml.silence@gmail.com


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