Add useVrFlinger() method to SurfaceFlinger ConfigStore

Add useVrFlinger() method to SurfaceFlinger ConfigStore, which is
used to ensure we only start vr flinger on Daydream ready devices.

Bug: 35885165

Test: Checked for "SurfaceFlinger UseVrFlinger" in the logs,
confirmed it only shows up for Daydream ready devices.

Change-Id: I3c39b1f094e28f06b510171fc0968cf71f5d5550
4 files changed