gl_rasterizer: Skip VAO binding if the state is clean.

src/video_core/engines/maxwell_3d.h

@@ -983,6 +983,12 @@ public:
     State state{};
     MemoryManager& memory_manager;
 
+    struct DirtyFlags {
+        bool vertex_attrib_format = true;
+    };
+
+    DirtyFlags dirty_flags;
+
     /// Reads a register value located at the input method address
     u32 GetRegisterValue(u32 method) const;