Allow new preamble in vblock for Alex firmware

This is a cherry-pick of the change in
http://gerrit.chromium.org/gerrit/#change,5212,patchset=11.

BUG=chrome-os-partner:5894
TEST=Run HWID validation test

Change-Id: I9da44242330ddf433173a63006b11edb4ade62aa
Reviewed-on: http://gerrit.chromium.org/gerrit/7470
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: Jay Kim <yongjaek@chromium.org>
1 file changed