hwc2: open and close hwc2 device

Add support for opening/closing a hardware composer v2.0 device described in
hardware/hwcomposer2.h

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: Id31114d6c38090e37f2bb6e508594646c382493b
6 files changed