io_uring/iopoll: fix unexpected returns

We may propagate a positive return value of io_run_task_work() out of
io_iopoll_check(), which breaks our tests. io_run_task_work() doesn't
return anything useful for us, ignore the return value.

Fixes: c0e0d6ba ("io_uring: add IORING_SETUP_DEFER_TASKRUN")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/c442bb87f79cea10b3f857cbd4b9a4f0a0493fa3.1662652536.git.asml.silence@gmail.com


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