io_uring: simplify io_has_work

->work_llist should never be non-empty for a non DEFER_TASKRUN ring, so
we can safely skip checking the flag.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/26af9f73c09a56c9a035f94db56127358688f3aa.1672916894.git.asml.silence@gmail.com


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