sf: Execute hwc power state change asynchronously

- Call into HWC to change hardware power state first, followed by
  surfaceflinger power state while stepping up
  i.e. off -> on, dozesuspend -> doze/on.
- Let surfaceflinger power state change happen first, followed by
  hardware power state while stepping down
  i.e. on -> off, doze/on -> dozesuspend.

CRs-Fixed: 2462237
Change-Id: Id3443594055713c1ed82330c0b31696c629fd47d