Sync with a recent liburing fix, which corrects the comment explaining
when the IORING_SETUP_TASKRUN_FLAG setup flag is valid to use. May be
use with COOP_TASKRUN or DEFER_TASKRUN, not useful without either of
this task_work mechanisms being used.
Link: https://github.com/axboe/liburing/pull/1543
Signed-off-by: Jens Axboe <axboe@kernel.dk>