[revert] remove rt_thread_exit
@@ -151,7 +151,6 @@ rt_err_t rt_thread_mdelay(rt_int32_t ms);
rt_err_t rt_thread_control(rt_thread_t thread, int cmd, void *arg);
rt_err_t rt_thread_suspend(rt_thread_t thread);
rt_err_t rt_thread_resume(rt_thread_t thread);
-void rt_thread_exit(void);
void rt_thread_timeout(void *parameter);
#ifdef RT_USING_SIGNALS
