drm_hwcomposer: Rework display Mode Setting and DPMS handling

1. Remove DPMS logic. As stated in KMS kernel docs: CRTC "activate"
   property was implemented as a simplified atomic replacement of DPMS.
   And kernel internally will just update "activate" on DPMS setting.

2. Add SetDisplayActivate(bool state) method to compositor class,
   which is now replacement for SetDpmsMode().

3. Move mode settings out of DrmComposition class to DrmCompositor class.
   From now on DrmComposition describes only layer-to-plane composition
   as it should be.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/compositor/DrmDisplayCompositor.h b/compositor/DrmDisplayCompositor.h
index 3227e12..e76abf7 100644
--- a/compositor/DrmDisplayCompositor.h
+++ b/compositor/DrmDisplayCompositor.h
@@ -44,8 +44,13 @@
   std::unique_ptr<DrmDisplayComposition> CreateInitializedComposition() const;
   int ApplyComposition(std::unique_ptr<DrmDisplayComposition> composition);
   int TestComposition(DrmDisplayComposition *composition);
-  int Composite();
   void ClearDisplay();
+  auto SetDisplayMode(const DrmMode &display_mode) -> bool;
+  auto SetDisplayActive(bool state) -> void {
+    active_ = state;
+    active_changed_ = true;
+  }
+
   UniqueFd TakeOutFence() {
     if (!active_composition_) {
       return UniqueFd();
@@ -65,12 +70,8 @@
   DrmDisplayCompositor(const DrmDisplayCompositor &) = delete;
 
   int CommitFrame(DrmDisplayComposition *display_comp, bool test_only);
-  int ApplyDpms(DrmDisplayComposition *display_comp);
   int DisablePlanes(DrmDisplayComposition *display_comp);
 
-  void ApplyFrame(std::unique_ptr<DrmDisplayComposition> composition,
-                  int status);
-
   auto CreateModeBlob(const DrmMode &mode) -> DrmModeUserPropertyBlobUnique;
 
   ResourceManager *resource_manager_;
@@ -79,8 +80,7 @@
   std::unique_ptr<DrmDisplayComposition> active_composition_;
 
   bool initialized_;
-  bool active_;
-  bool use_hw_overlays_;
+  bool active_{true}, active_changed_{true};
 
   ModeState mode_;