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

[Cliff Huang (Code Review)]

Attention is currently required from: Anil Kumar K, Bora Guvendik, Julius Werner, Jérémy Compostella, Subrata Banik, Wonkyu Kim.

Cliff Huang has posted comments on this change by Cliff Huang. ( https://review.coreboot.org/c/coreboot/+/83153?usp=email )

Change subject: src/lib: Add Kconfig variable for fw_config default value
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Patch Set 3:

(2 comments)

Patchset:

PS2:
> If fw_config_value is all '1's, fw_config_is_provisioned() returns false. […]

Please see my other comment and patch set 3 for new changes.

File src/Kconfig:

https://review.coreboot.org/c/coreboot/+/83153/comment/be42a301_c0fc28b8?usp... :
PS2, Line 548: 0x00000
> Good point! This is used in make build environment where no CBI value is synced from config.star. […]

I change default value to UNDEFINED_FW_CONFIG and this won't be used unless config.<board> has different value. We are using this to assign fw_config value in make build environment and using simulation environment.