add actled biling

bsp/raspberry-pi/raspi4-32/applications/main.c

@@ -12,8 +12,20 @@
 #include <rtdevice.h>
 #include <board.h>
 
+#define     ACTLED      (42)
+
 int main(int argc, char** argv)
 {
     rt_kprintf("Hi, this is RT-Thread!!\n");
-    return 0;
+    
+    rt_pin_mode(ACTLED, PIN_MODE_OUTPUT);
+
+    while(1)
+    {
+        rt_pin_write(ACTLED, PIN_HIGH);
+        rt_thread_mdelay(1000);
+        rt_pin_write(ACTLED, PIN_LOW);
+        rt_thread_mdelay(1000);
+    }
+    return RT_EOK;
 }