io_uring: mainstream sqpoll task_work running

task_works are widely used, so place io_run_task_work() directly into
the main path of io_sq_thread(), and remove it from other places where
it's not needed anymore.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/24eb5e35d519c590d3dffbd694b4c61a5fe49029.1624739600.git.asml.silence@gmail.com


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