hwc2: get and set active config

Client can get and set the active config

Test: Add "TARGET_USES_HWC2 := true" to BoardConfig.mk.
      Recompile.
      Run testcases: https://android-review.googlesource.com/#/q/project:
            platform/frameworks/native+branch:master+topic:test-hwc2

Change-Id: Ic506b1afb22706d71be8be2fe49056248f0bfb1e
4 files changed