io_uring/net: add IORING_SEND_IGNORE_INLINE support to zerocopy send

io_uring/net: add IORING_SEND_IGNORE_INLINE support to zerocopy send

If IORING_SEND_IGNORE_INLINE is set for a send zerocopy request, then a
successful inline completion of such a request will be ignored for a
submit_and_wait() type of submissions. In other words, if an application
submits a send for socketA with a recv for socketB, it can now do:

io_uring_submit_and_wait(ring, 1);

and have the inline send completion be ignored from the number of items
to wait for. Note that this only applies to the direct zerocopy send
completion, it does not include the notification when it's safe to reuse
the buffer. Those happen out-of-line anyway.

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