add mqttclient to the component, and add fire stm32f429 board demo.

components/connectivity/mqttclient/platform/TencentOS-tiny/platform_timer.h

@@ -0,0 +1,25 @@
+/*
+ * @Author: jiejie
+ * @Github: https://github.com/jiejieTop
+ * @Date: 2019-12-10 22:18:32
+ * @LastEditTime : 2020-01-11 01:20:44
+ * @Description: the code belongs to jiejie, please keep the author information and source code according to the license.
+ */
+#ifndef _PLATFORM_TIMER_H_
+#define _PLATFORM_TIMER_H_
+
+#include "tos_k.h"
+
+
+typedef struct platform_timer {
+    uint32_t time;
+} platform_timer_t;
+
+void platform_timer_init(platform_timer_t* timer);
+void platform_timer_cutdown(platform_timer_t* timer, unsigned int timeout);
+char platform_timer_is_expired(platform_timer_t* timer);
+int platform_timer_remain(platform_timer_t* timer);
+unsigned long platform_timer_now(void);
+void platform_timer_usleep(unsigned long usec);
+
+#endif