vboot2: Add routines to load kernel preamble

The kernel data itself will be read and verified by a subsequent
change.

BUG=chromium:487699
BRANCH=none
TEST=make -j runtests

Change-Id: Ife4f8250493ec6457f91fda57ae8d4d7bf18ec89
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/274038
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
6 files changed