sdl: remove unused variable

Variable rec is not used, remove it. Spotted by GCC 4.6.0:
  CC    ui/sdl.o
/src/qemu/ui/sdl.c: In function 'sdl_setdata':
/src/qemu/ui/sdl.c:90:14: error: variable 'rec' set but not used [-Werror=unused-but-set-variable]
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

ui/sdl.c

@@ -87,12 +87,6 @@ static void sdl_update(DisplayState *ds, int x, int y, int w, int h)
 
 static void sdl_setdata(DisplayState *ds)
 {
-    SDL_Rect rec;
-    rec.x = 0;
-    rec.y = 0;
-    rec.w = real_screen->w;
-    rec.h = real_screen->h;
-
     if (guest_screen != NULL) SDL_FreeSurface(guest_screen);
 
     guest_screen = SDL_CreateRGBSurfaceFrom(ds_get_data(ds), ds_get_width(ds), ds_get_height(ds),