cpu: Move call to stop_machine_unpark()

This is Peter's candidate fix for the workqueues splat from heavy
rcutorture testing.

Link: https://lore.kernel.org/lkml/20191203095521.GH2827@hirez.programming.kicks-ass.net/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
1 file changed