simple-egl: Clean up unused frame_listener

Unused since commit 1e65840b61

Signed-off-by: Boyan Ding <stu_dby@126.com>
Reviewed-by: Nils Chr. Brause <nilschrbrause@gmail.com>

clients/simple-egl.c

@@ -367,8 +367,6 @@ destroy_surface(struct window *window)
 		wl_callback_destroy(window->callback);
 }
 
-static const struct wl_callback_listener frame_listener;
-
 static void
 redraw(void *data, struct wl_callback *callback, uint32_t time)
 {
@@ -469,10 +467,6 @@ redraw(void *data, struct wl_callback *callback, uint32_t time)
 	window->frames++;
 }
 
-static const struct wl_callback_listener frame_listener = {
-	redraw
-};
-
 static void
 pointer_handle_enter(void *data, struct wl_pointer *pointer,
 		     uint32_t serial, struct wl_surface *surface,