drm_hwcomposer: CI: Set clang-tidy level to NORMAL for some files

Some of files require small adjustments to move into NORMAL checks list.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/backend/BackendManager.cpp b/backend/BackendManager.cpp
index 7b89761..36fb55f 100644
--- a/backend/BackendManager.cpp
+++ b/backend/BackendManager.cpp
@@ -49,7 +49,7 @@
   std::string backend_name(backend_override);
 
   display->set_backend(GetBackendByName(backend_name));
-  if (!display->backend()) {
+  if (display->backend() == nullptr) {
     ALOGE("Failed to set backend '%s' for '%s' and driver '%s'",
           backend_name.c_str(), display->connector()->name().c_str(),
           driver_name.c_str());