Eliminate superfluous 'setDirty' call.

src/common/FBSurfaceSDL2.hxx

@@ -41,8 +41,6 @@ class FBSurfaceSDL2 : public FBSurface
     // the ones implemented here use SDL-specific code for extra performance
     //
     void fillRect(uInt32 x, uInt32 y, uInt32 w, uInt32 h, ColorId color) override;
-    // With hardware surfaces, it's faster to just update the entire surface
-    void setDirty() override {}
 
     uInt32 width() const override;
     uInt32 height() const override;

src/emucore/FBSurface.hxx

@@ -350,12 +350,6 @@ class FBSurface
     static void setPalette(const uInt32* palette) { myPalette = palette; }
 
   protected:
-    /**
-      This method must be called to indicate that the surface has been
-      modified, and should be redrawn at the next interval.
-    */
-    virtual void setDirty() = 0;
-
     /**
       This method should be called to check if the given coordinates
       are in bounds of the surface.

src/libretro/FBSurfaceLIBRETRO.hxx

@@ -37,7 +37,6 @@ class FBSurfaceLIBRETRO : public FBSurface
 
     // Most of the surface drawing primitives are implemented in FBSurface;
     void fillRect(uInt32 x, uInt32 y, uInt32 w, uInt32 h, ColorId color) override { }
-    void setDirty() override { }
 
     uInt32 width() const override { return myWidth; }
     uInt32 height() const override { return myHeight; }