Change ROM hash calculation to trust FMAP

Allowing the FMAP to override our default layout may be an exploit here, because
vendor can provide fake (non-used) GBB/BSTUB in unused area.
However since the flash memory layout may change, we need to trust FMAP.

BUG=chrome-os-partner:920
TEST=none

Change-Id: Icabd2febb04930a024ef5800ee09e3436de724ab

Review URL: http://codereview.chromium.org/3328013
1 file changed