drm_hwcomposer: clang-tidy: enable cppcoreguidelines-* checks

Our code isn't ready for the following checks therefore keep disabled
-cppcoreguidelines-pro-bounds-array-to-pointer-decay
-cppcoreguidelines-pro-bounds-constant-array-index
-cppcoreguidelines-pro-bounds-pointer-arithmetic
-cppcoreguidelines-pro-type-cstyle-cast
-cppcoreguidelines-pro-type-vararg
-cppcoreguidelines-avoid-magic-numbers
-cppcoreguidelines-macro-usage
-cppcoreguidelines-avoid-c-arrays

+ fixed existing tidy warnings for these checks.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/compositor/DrmDisplayComposition.cpp b/compositor/DrmDisplayComposition.cpp
index a8dc0fc..ef151a1 100644
--- a/compositor/DrmDisplayComposition.cpp
+++ b/compositor/DrmDisplayComposition.cpp
@@ -103,7 +103,7 @@
   for (size_t i = 0; i < layers_.size(); ++i)
     to_composite.emplace(std::make_pair(i, &layers_[i]));
 
-  int ret;
+  int ret = 0;
   std::tie(ret,
            composition_planes_) = planner_->ProvisionPlanes(to_composite, crtc_,
                                                             primary_planes,
@@ -122,7 +122,7 @@
     // make sure that source layers are ordered based on zorder
     std::sort(i.source_layers().begin(), i.source_layers().end());
 
-    std::vector<DrmPlane *> *container;
+    std::vector<DrmPlane *> *container = nullptr;
     if (i.plane()->type() == DRM_PLANE_TYPE_PRIMARY)
       container = primary_planes;
     else