io_uring/net: rename io_uring_tx_zerocopy_callback

Just a simple renaming patch, io_uring_tx_zerocopy_callback() is too
bulky and doesn't follow usual naming style.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/24d78325403ca6dcb1ec4bced1e33cacc9b832a5.1667557923.git.asml.silence@gmail.com


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