io_uring: move timeout locking in io_timeout_cancel()

Move ->timeout_lock grabbing inside of io_timeout_cancel(), so
we can do io_req_task_queue_fail() outside of the lock. It's much nicer
than relying on triple nested locking.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cde758c2897930d31e205ed8f476d4ec879a8849.1650458197.git.asml.silence@gmail.com


[axboe: drop now wrong timeout_lock annotation]
Signed-off-by: Jens Axboe <axboe@kernel.dk>