io_uring/poll: lockdep annote io_poll_req_insert_locked

Add a lockdep annotation in io_poll_req_insert_locked().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8115d8e702733754d0aea119e9b5bb63d1eb8b24.1668184658.git.asml.silence@gmail.com


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