We waste a u64 SQE field for flags even though we don't need as many
bits and it can be used for something more useful later. Store io_uring
specific send/recv flags in sqe->ioprio instead of ->addr2.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Fixes: 6bb2c14111c3 ("io_uring: add POLL_FIRST support for send/sendmsg and recv/recvmsg")
[axboe: change comment in io_uring.h as well] Signed-off-by: Jens Axboe <axboe@kernel.dk>