fix typo

you meant fps, not LEDs here, right?

and a question: is this an "official" fork of the osresearch library? or are you still pushing things upstream eventually? if its meant to be a fork, a quick note in the README would help, and maybe also opening the issues feature on github.

i am planning a project with around 20k LEDs and so far the beagleboard with LEDscape looks the most promising option...