drm_hwcomposer: CI: Process every file with clang-tidy.

Currently part of header files isn't processed by CI.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/drm/DrmPlane.h b/drm/DrmPlane.h
index 34bba56..7fab2ba 100644
--- a/drm/DrmPlane.h
+++ b/drm/DrmPlane.h
@@ -29,6 +29,7 @@
 namespace android {
 
 class DrmDevice;
+struct DrmHwcLayer;
 
 class DrmPlane {
  public: