hwc2: enable the vsync on the display requested by SF

-- Avoid calculating the next vsync source based on the
  active display list in hwc2.
-- Enable/disable the vsync on the HWC display as requested
  by SurfaceFlinger.

Change-Id: I901be3d06ad1102d30232e6fb8dbb0d1709b5a68
CRs-fixed: 2429625
7 files changed