Bring in upstream changes

This brings in changes to our tree from the upstream seabios. It is taken
from commit f21b5a4a.

This is merge commit.

BUG=chromium:1034094
TEST=with other CLs
USE=seabios emerge-zork chromeos-bootimage
See that we get a booting image

Cq-Depend: chromium:1976517
Change-Id: I1c2d89ab0200744c6f4b6202c5c1f76bec25bcab