drm_hwcomposer: CI: Raise clang-tidy level from NONE to COARSE for *.h

To improve CI coverage.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/compositor/DrmDisplayComposition.h b/compositor/DrmDisplayComposition.h
index cbc0a90..d077aee 100644
--- a/compositor/DrmDisplayComposition.h
+++ b/compositor/DrmDisplayComposition.h
@@ -52,7 +52,7 @@
   }
 
  private:
-  DrmPlane *plane_ = NULL;
+  DrmPlane *plane_ = nullptr;
   size_t source_layer_ = kUndefinedSourceLayer;
 };
 
@@ -85,8 +85,8 @@
   }
 
  private:
-  DrmCrtc *crtc_ = NULL;
-  Planner *planner_ = NULL;
+  DrmCrtc *crtc_ = nullptr;
+  Planner *planner_ = nullptr;
 
   std::vector<DrmHwcLayer> layers_;
   std::vector<DrmCompositionPlane> composition_planes_;
diff --git a/compositor/DrmDisplayCompositor.h b/compositor/DrmDisplayCompositor.h
index f6333eb..41e708f 100644
--- a/compositor/DrmDisplayCompositor.h
+++ b/compositor/DrmDisplayCompositor.h
@@ -63,9 +63,9 @@
 
   auto ExecuteAtomicCommit(AtomicCommitArgs &args) -> int;
 
- private:
   DrmDisplayCompositor(const DrmDisplayCompositor &) = delete;
 
+ private:
   auto CommitFrame(AtomicCommitArgs &args) -> int;
 
   struct KmsState {
diff --git a/compositor/Planner.h b/compositor/Planner.h
index ff059f5..c148b6e 100644
--- a/compositor/Planner.h
+++ b/compositor/Planner.h
@@ -36,7 +36,7 @@
   // Removes and returns the next available plane from planes
   static DrmPlane *PopPlane(std::vector<DrmPlane *> *planes) {
     if (planes->empty())
-      return NULL;
+      return nullptr;
     DrmPlane *plane = planes->front();
     planes->erase(planes->begin());
     return plane;