video_core/engines: Make memory manager members private

These aren't used externally by anything, so they can be made private
data members.

src/video_core/engines/maxwell_3d.h

@@ -1096,7 +1096,6 @@ public:
     };
 
     State state{};
-    MemoryManager& memory_manager;
 
     struct DirtyFlags {
         std::bitset<8> color_buffer{0xFF};
@@ -1144,6 +1143,8 @@ private:
 
     VideoCore::RasterizerInterface& rasterizer;
 
+    MemoryManager& memory_manager;
+
     /// Start offsets of each macro in macro_memory
     std::unordered_map<u32, u32> macro_offsets;