io_uring: keep io_put_req only responsible for release and put req

We already have io_put_req_find_next to find the next req of the link.
we should not use the io_put_req function to find them. They should be
functions of the same level.

Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>