Crochet Updates for RPi, BeagleBone

[Tim Kientzle]

I just committed changes to Crochet so that it now uses the U-Boot ports for RPi and BeagleBone (including BBB).  It already used the port for RPi2.

If people want to change other boards, you can use the RPi, RPi2, or BeagleBone configurations as examples.  Generally, switching to using a port does seem to simplify the code.

Let me know if you run into any problems…

Tim