rpi4_out.cpp: moved thread_id to correct structure

src/video_display/rpi4_out.cpp

@@ -167,8 +167,6 @@ private:
         mmal_component_unique renderer_component;
         mmal_pool_unique pool;
         av_zc_env_unique zero_copy_env;
-
-        std::thread thread_id;
 };
 
 void Rpi4_video_out::resize(int width, int height){
@@ -361,6 +359,8 @@ struct rpi4_display_state{
         std::mutex free_frames_mut;
         std::stack<unique_frame> free_frames;
 
+        std::thread thread_id;
+
         int requested_pos_x = 0;
         int requested_pos_y = 0;
         int force_w = 0;