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/Planner.cpp b/compositor/Planner.cpp
index fb6a8c3..b6f10d2 100644
--- a/compositor/Planner.cpp
+++ b/compositor/Planner.cpp
@@ -45,7 +45,7 @@
 
 int Planner::PlanStage::ValidatePlane(DrmPlane *plane, DrmHwcLayer *layer) {
   int ret = 0;
-  uint64_t blend;
+  uint64_t blend = UINT64_MAX;
 
   if ((plane->rotation_property().id() == 0) &&
       layer->transform != DrmHwcTransform::kIdentity) {
@@ -122,7 +122,7 @@
     std::vector<DrmCompositionPlane> *composition,
     std::map<size_t, DrmHwcLayer *> &layers, DrmCrtc *crtc,
     std::vector<DrmPlane *> *planes) {
-  int ret;
+  int ret = 0;
   for (auto i = layers.begin(); i != layers.end();) {
     if (!i->second->protected_usage()) {
       ++i;