io_uring: refactor lazy link fail

Remove the lazy link fail logic from io_submit_sqe() and hide it into a
helper. It simplifies the code and will be needed in next patches.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/6a68aca9cf4492132da1d7c8a09068b74aba3c65.1650056133.git.asml.silence@gmail.com


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