add event-driven framework

see examples/event_driven_at_module and examples/event_driven_hello_world, demo project: TencentOS-tiny\board\TencentOS_tiny_EVB_MX\KEIL\event_driven_hello_world

kernel/evtdrv/tos_evtdrv_tick.c

@@ -0,0 +1,36 @@
+#include "tos_evtdrv.h"
+
+#if TOS_CFG_EVENT_DRIVEN_EN > 0u
+
+__API__ evtdrv_time_t tos_evtdrv_tick2millisec(evtdrv_tick_t tick)
+{
+    return (evtdrv_time_t)(tick * EVTDRV_TIME_MILLISEC_PER_SEC / TOS_CFG_CPU_TICK_PER_SECOND);
+}
+
+__API__ evtdrv_tick_t tos_evtdrv_millisec2tick(evtdrv_time_t ms)
+{
+    return ((evtdrv_tick_t)ms * TOS_CFG_CPU_TICK_PER_SECOND / EVTDRV_TIME_MILLISEC_PER_SEC);
+}
+
+__API__ evtdrv_tick_t tos_evtdrv_systick_get(void)
+{
+    TOS_CPU_CPSR_ALLOC();
+    evtdrv_tick_t tick;
+
+    TOS_CPU_INT_DISABLE();
+    tick = evtdrv_tick_count;
+    TOS_CPU_INT_ENABLE();
+    return tick;
+}
+
+__API__ void tos_evtdrv_tick_handler(void)
+{
+    TOS_CPU_CPSR_ALLOC();
+
+    TOS_CPU_INT_DISABLE();
+    ++evtdrv_tick_count;
+    TOS_CPU_INT_ENABLE();
+}
+
+#endif
+