ANDROID: stop_machine: stop_one_cpu_async

This new interface allows to trigger a stopper on a given CPU and wait
for the end of the work in a separated function cpu_stop_work_wait().

This differs from stop_one_cpu_nowait() by allowing the usage of the
cpu_stop completion mechanism.

Bug: 161210528
Change-Id: Ida51371e32897d008ece0639190fc21feabb0f28
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>