directfb: Changed internal function to be static.

src/video/directfb/SDL_DirectFB_render.c

@@ -332,7 +332,7 @@ DirectFB_WindowEvent(SDL_Renderer * renderer, const SDL_WindowEvent *event)
    }
 }
 
-int
+static int
 DirectFB_RenderClear(SDL_Renderer * renderer)
 {
     DirectFB_RenderData *data = (DirectFB_RenderData *) renderer->driverdata;
@@ -344,7 +344,6 @@ DirectFB_RenderClear(SDL_Renderer * renderer)
 
     destsurf->Clear(destsurf, renderer->r, renderer->g, renderer->b, renderer->a);
 
-
     return 0;
 }