ich_descriptors: Add function to guess chipset version

Add guess_ich_chipset() that takes fields from a descriptor dump and
returns the lowest possible chipset version.

Intel did several incompatible changes to the descriptor through the
years. However, they forgot to add a version number. So we have to
apply some heuristics to detect the chipset version in case of exter-
nal flashing.

Change-Id: Ie1736663dc33801b19d3e695c072c61a6c6345a2
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20246
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
2 files changed