Corrected 'sussystem' to 'subsystem'

examples/blinky/blinky.c

@@ -23,7 +23,7 @@ void some_timerfunc(void *arg)
 
 void ICACHE_FLASH_ATTR user_init()
 {
-  // init gpio sussytem
+  // init gpio subsytem
   gpio_init();
 
   // configure UART TXD to be GPIO1, set as output