dts: am335x-bone-common: fixup leds to match 3.8

https://groups.google.com/d/msg/beagleboard/634Xm1m3XA8/B028x1FzAyAJ



Reported-by: Mark A. Yoder <mark.a.yoder@gmail.com>
Signed-off-by: Robert Nelson <robertcnelson@gmail.com>