video_core: Fine tuning the index drawing judgment logic

src/video_core/engines/maxwell_3d.h

@@ -3182,6 +3182,7 @@ private:
     std::vector<u32> deferred_draw_method;
     enum class DrawMode : u32 { General = 0, Instance, InlineIndex };
     DrawMode draw_mode{DrawMode::General};
+    bool draw_indexed{};
 };
 
 #define ASSERT_REG_POSITION(field_name, position)                                                  \