image_signing: drop board hacking for lsb appid checks
image_signing: drop board hacking for lsb appid checks

BUG=chromium:605595
TEST=None
BRANCH=None

Change-Id: I8104d80d151440bdd8f419c88bd98592d9f44612
Reviewed-on: https://chromium-review.googlesource.com/371678
Commit-Ready: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Hung-Te Lin <8a7fce4940baad93a69f5073b383c85deed9d9c4@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot