"led toggle" doesn't quite toggle leds on beagle xM

i mentioned this to jason kridner yesterday since he's the official
author of cmd_led.c in u-boot and i may try to debug later today but
if anyone wants to beat me to it ...

  master repo u-boot build for beagle, running on my xM (rev C):

led [0|1|all] works fine
led [0|1|all] toggle toggles only if led(s) already off

just making an observation.