msm: hotplug: Rewrite suspend-resume

* Use power-suspend instead of LCD notifier, power-suspend being
  less aggressive comparatively.
* When suspended, flush workqueue and put all sibling cores to rest.
  (yin-yan is complete as resume fires up all cores for downlock
   duration.)
* This should help to save little more battery.
* Additionally, it will help to save power and generate less heat
  when min_cpus_online > 1.

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>