io_uring: move kbuf put out of generic tw complete

There are multiple users of io_req_task_complete() including zc
notifications, but only read requests use selected buffers. As we
already have an rw specific tw function, move io_put_kbuf() in there.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/94374c7649aaefc3a17808dc4701f25ccd457e25.1667557923.git.asml.silence@gmail.com


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