OpcodeDecoding: Get vertex size from the loader

Source/Core/VideoCommon/OpcodeDecoding.cpp

@@ -228,6 +228,12 @@ public:
       return g_main_cp_state;
   }
 
+  OPCODE_CALLBACK(u32 GetVertexSize(u8 vat))
+  {
+    VertexLoaderBase* loader = VertexLoaderManager::RefreshLoader<is_preprocess>(vat);
+    return loader->m_vertex_size;
+  }
+
   u32 m_cycles = 0;
   bool m_in_display_list = false;
 };