io_uring: update sq_thread_idle after ctx deleted

we shall update sq_thread_idle anytime we do ctx deletion from ctx_list

Fixes:734551df ("io_uring: fix shared sqpoll cancellation hangs")

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/1619256380-236460-1-git-send-email-haoxu@linux.alibaba.com


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