[LED] init 8 leds and a periodic timer function by
void rt_hw_led(rt_uint8_t led, rt_uint16_t ticks, rt_uint8_t on,
rt_uint32_t cnt)
finsh is supported by
void setled(rt_uint8_t led, rt_uint16_t ticks, rt_uint8_t on, rt_uint32_t
cnt)