Updated Chromebook ARM Wiki Page

[Michael Dexter]

Hello all,

I have rewritten the Chromebook ARM wiki page to focus on USB boot which 
allows for self-hosing:

https://wiki.freebsd.org/FreeBSD/arm/Chromebook

A kernel build takes about 14 minutes and 30 seconds on the Samsung 
Chromebook 1 and I welcome your tests and input with the Chromebook2 
"Peach Pit" and HP Chromebook 11 "Spring".

Please CC me responses as I am not subscribed to the list yet.

Michael Dexter