io_uring: consistent typing for issue_flags

Some of the functions keep issue_flags as int, change those to unsigned.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/04ad43797783bc9cc7567f287ab545518f8e8cf2.1634144845.git.asml.silence@gmail.com


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