hwc2: display type support

Store each display's type and return it to the client on request

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: I6c1bfdfd589e756b4113f0d82cb2aa2745de9213
4 files changed