io_uring: add data_race annotations

We have several racy reads, mark them with data_race() to demonstrate
this fact.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7e56e750d294c70b2a56938bd733386f19f0eb53.1650056133.git.asml.silence@gmail.com


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