io_uring: remove extra io_ring_exit_work wake up

task_work_add() takes care of waking up the thread, remove useless
wake_up_process().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/de9a71ee255112dcaed3b5d426be24934e74722c.1633532552.git.asml.silence@gmail.com


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