drm_hwcomposer: Rework DrmMode class

Simplify code and raise-up clang-tidy level of DrmMode class
to 'normal'.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/hwc2_device/HwcDisplayConfigs.h b/hwc2_device/HwcDisplayConfigs.h
index 639b302..98067c1 100644
--- a/hwc2_device/HwcDisplayConfigs.h
+++ b/hwc2_device/HwcDisplayConfigs.h
@@ -29,11 +29,11 @@
 struct HwcDisplayConfig {
   uint32_t id{};
   uint32_t group_id{};
-  DrmMode mode;
+  DrmMode mode{};
   bool disabled{};
 
   bool IsInterlaced() const {
-    return (mode.flags() & DRM_MODE_FLAG_INTERLACE) != 0;
+    return (mode.GetRawMode().flags & DRM_MODE_FLAG_INTERLACE) != 0;
   }
 };