[M] Change in coreboot[main]: Support loading legacy stage

[Vladimir Serbinenko (Code Review)]

Attention is currently required from: Julius Werner.

Hello Julius Werner, build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/81505?usp=email

to look at the new patch set (#2).

The following approvals got outdated and were removed:
Verified+1 by build bot (Jenkins)

Change subject: Support loading legacy stage
......................................................................

Support loading legacy stage

This allows to create hybrid images that boot old signed stage
image in one of RW_A/RW_B and a newer RO with newer behaviour.
This allows to have dual-boot between stock ChromeOS and custom
coreboot

Change-Id: I4ae29a6227235c86f9f846986c18b361c3b3c78d
Signed-off-by: Vladimir Serbinenko 
---
M src/commonlib/bsd/include/commonlib/bsd/cbfs_serialized.h
M src/lib/cbfs.c
2 files changed, 78 insertions(+), 27 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/05/81505/2