Rather than match on a specific key, be it user_data or file, allow
canceling any request that we can lookup. Works like
IORING_ASYNC_CANCEL_ALL in that it cancels multiple requests, but it
doesn't key off user_data or the file.

Can't be set with IORING_ASYNC_CANCEL_FD, as that's a key selector.
Only one may be used at the time.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20220418164402.75259-6-axboe@kernel.dkSigned-off-by: Jens Axboe <axboe@kernel.dk>