Wiring up register read/write from JIT -> GPU.

src/xenia/gpu/nop/nop_graphics_system.h

@@ -25,6 +25,9 @@ class NopGraphicsSystem : public GraphicsSystem {
 public:
   NopGraphicsSystem(const CreationParams* params);
   virtual ~NopGraphicsSystem();
+
+  virtual uint64_t ReadRegister(uint32_t r);
+  virtual void WriteRegister(uint32_t r, uint64_t value);
 };