AbstractTexture: Return config by const reference

Returning by const value isn't really necessary (and usually an indicator const reference was intended).

Source/Core/VideoCommon/AbstractTexture.cpp

@@ -38,7 +38,7 @@ size_t AbstractTexture::CalculateHostTextureLevelPitch(AbstractTextureFormat for
   }
 }
 
-const TextureConfig AbstractTexture::GetConfig() const
+const TextureConfig& AbstractTexture::GetConfig() const
 {
   return m_config;
 }

Source/Core/VideoCommon/AbstractTexture.h

@@ -28,7 +28,7 @@ public:
   static bool IsCompressedHostTextureFormat(AbstractTextureFormat format);
   static size_t CalculateHostTextureLevelPitch(AbstractTextureFormat format, u32 row_length);
 
-  const TextureConfig GetConfig() const;
+  const TextureConfig& GetConfig() const;
 
 protected:
   const TextureConfig m_config;