vboot2: misc higher-level routines

I'm breaking the last chunk of vboot2 into smaller pieces as I add
tests.  This has a bunch of misc routines like the dev switch logic
and GBB header parsing.

TEST=make clean && VBOOT2=1 COV=1 make

Change-Id: I0f67400d9b59ec21ed5cc155a9b774fd37eb559b
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/203374
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
7 files changed