quick hack to use ACT LED for checking shutdown

[shigeru at os-hackers.jp]

Hi all,

I rewrite a patch to use ACT LED.
http://freebsd-current.os-hackers.jp/pub/FreeBSD/snapshots/20130816/raspberry-pi/patch-act_led-r254404.diff

A change of new patch is controling ACT LEd function by kernel
 environment ('hw.led.act').
For RaspberryPi, a value is "gpio:0:16:1:0" which means,
- on gpio0
- pin 16
- set 1 when LED off
- set 0 when LED on

Please check my patch if you are interested in it.

Thanks,
---
YAMAMOTO Shigeru <shigeru at os-hackers.jp>