VideoCommon: Drop FlipImageData.

This function isn't used any more, and good code shouldn't use it at all. Use negative strides instead.

Source/Core/VideoCommon/RenderBase.cpp

@@ -757,16 +757,3 @@ void Renderer::RunFrameDumps()
   }
 #endif
 }
-
-void Renderer::FlipImageData(u8* data, int w, int h, int pixel_width)
-{
-  for (int y = 0; y < h / 2; ++y)
-  {
-    for (int x = 0; x < w; ++x)
-    {
-      for (int delta = 0; delta < pixel_width; ++delta)
-        std::swap(data[(y * w + x) * pixel_width + delta],
-                  data[((h - 1 - y) * w + x) * pixel_width + delta]);
-    }
-  }
-}

Source/Core/VideoCommon/RenderBase.h

@@ -122,8 +122,6 @@ public:
   virtual u16 BBoxRead(int index) = 0;
   virtual void BBoxWrite(int index, u16 value) = 0;
 
-  static void FlipImageData(u8* data, int w, int h, int pixel_width = 3);
-
   // Finish up the current frame, print some stats
   static void Swap(u32 xfbAddr, u32 fbWidth, u32 fbStride, u32 fbHeight, const EFBRectangle& rc,
                    u64 ticks, float Gamma = 1.0f);