hwc2: power mode support

Allow client to set power mode to on or off. Doze modes are not currently
supported.

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: Ia4d579b28ac725975248eacd82685155ae7b0d91
4 files changed