Migrate SConfig::bWii to System.

Source/Core/Core/System.h

@@ -136,8 +136,10 @@ public:
   bool IsMMUMode() const { return m_mmu_enabled; }
   bool IsPauseOnPanicMode() const { return m_pause_on_panic_enabled; }
   bool IsMIOS() const { return m_is_mios; }
+  bool IsWii() const { return m_is_wii; }
 
   void SetIsMIOS(bool is_mios) { m_is_mios = is_mios; }
+  void SetIsWii(bool is_wii) { m_is_wii = is_wii; }
 
   SoundStream* GetSoundStream() const;
   void SetSoundStream(std::unique_ptr<SoundStream> sound_stream);
@@ -192,5 +194,6 @@ private:
   bool m_mmu_enabled = false;
   bool m_pause_on_panic_enabled = false;
   bool m_is_mios = false;
+  bool m_is_wii = false;
 };
 }  // namespace Core