[S] Change in coreboot[main]: lib: Add Kconfig variable for fw_config default value

[Cliff Huang (Code Review)]

Attention is currently required from: Anil Kumar K, Bora Guvendik, Cliff Huang, Julius Werner, Wonkyu Kim.

Hello Anil Kumar K, Bora Guvendik, Jérémy Compostella, Subrata Banik, Wonkyu Kim, build bot (Jenkins),

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

https://review.coreboot.org/c/coreboot/+/83153?usp=email

to look at the new patch set (#7).

Change subject: lib: Add Kconfig variable for fw_config default value
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lib: Add Kconfig variable for fw_config default value

This CONFIG_FW_CONFIG_DEFAULT_VALUE is used only when CBI fw_config
value cannot be read from all sources such as Chrome EC and VPD.
When CBI fw_config is not read successfully, fw_config_get returns
UNDEFINED_FW_CONFIG (i.e. all '1's) and all fw_config_probe calls will
fail. This flag dose not serve as a solution but a way to provide a
valid value for validation to move forward at early development period
in case Chrome EC communication has issue or the absence of EC in the
simulation environment. This flag defaults to the same value as
UNDEFINED_FW_CONFIG defined in fw_config.h; and it won't be used unless
it is set to different value in config.<board> file. If a valid value is
read from the Chrome EC or VPD, the fw_config value will not be
overridden by this flag.

TEST=boot and check fw_config value from coreboot log

Signed-off-by: Cliff Huang 
Change-Id: I9694433e01bdcd9ff1e550585c14ea7ccee020a3
---
M src/Kconfig
M src/lib/fw_config.c
2 files changed, 16 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/53/83153/7