Add Gale servo overlay and correct power cycle/usb boot procedure.

BUG=b:28656235
TEST=built an image and tested on Servo v3
Change-Id: I8aecc658f797e7db29892a2dcc9b120ce3e6915e
Reviewed-on: https://chromium-review.googlesource.com/347072
Commit-Ready: John Carey <ranix@google.com>
Tested-by: John Carey <ranix@google.com>
Reviewed-by: John Carey <ranix@google.com>
Reviewed-by: Kevin Cheng <kevcheng@chromium.org>
Reviewed-by: Laurence Goodby <lgoodby@chromium.org>
3 files changed