Nobody cares about io_run_task_work_sig returning 1, we only check for
negative errors. Simplify by keeping to 0/-error returns.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/3aec8a532c003d6e50739b969a82989402696170.1691757663.git.asml.silence@gmail.com


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