Add Init() in DummyuLittleVgl to fix recovery firmware

src/displayapp/DummyLittleVgl.h

@@ -19,6 +19,10 @@ namespace Pinetime {
       LittleVgl(LittleVgl&&) = delete;
       LittleVgl& operator=(LittleVgl&&) = delete;
 
+      void Init() {
+
+      }
+
       void FlushDisplay(const lv_area_t* area, lv_color_t* color_p) {
       }
       bool GetTouchPadInfo(lv_indev_data_t* ptr) {