Fix incorrect handling of auto IR

Some lines of code in Dolphin just plainly grabbed the value of
g_ActiveConfig.iEFBScale, which resulted in Auto being treated as
0x rather than the actual automatically selected scale.

Source/Core/VideoCommon/RenderBase.h

@@ -101,6 +101,8 @@ public:
   std::tuple<TargetRectangle, TargetRectangle>
   ConvertStereoRectangle(const TargetRectangle& rc) const;
 
+  unsigned int GetEFBScale() const;
+
   // Use this to upscale native EFB coordinates to IDEAL internal resolution
   int EFBToScaledX(int x) const;
   int EFBToScaledY(int y) const;