Add gpiod.c for libgpiod output sample code

guowenxue

2021-01-23 7baed996272cd3c889a5ab714c2b3391703f75f1

 mqttd/hal/hal.h

@@ -22,6 +22,7 @@
#include "ds18b20.h"
#include "sht20.h"
#include "tsl2561.h"
#include "beep.h"

#define OFF   0
#define ON    1