io_uring/net: use right helpers for async recycle

We have a helper that checks for whether a request contains anything in
->async_data or not, namely req_has_async_data(). It's better to use it
as it might have some extra considerations.

Fixes: 43e0bbbd ("io_uring: add netmsg cache")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b7414da4e7c3c32c31fc02dfd1355af4ccf4ca5f.1660566179.git.asml.silence@gmail.com


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