Change in coreboot[master]: soc/amd/cezanne: Add modern standby option to chip config

[Mathew King (Code Review)]

Attention is currently required from: Jason Glenesk, Raul Rangel, Furquan Shaikh, Felix Held.
Mathew King has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52041 )

Change subject: soc/amd/cezanne: Add modern standby option to chip config
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Patch Set 6:

(1 comment)

File src/soc/amd/cezanne/Kconfig:

https://review.coreboot.org/c/coreboot/+/52041/comment/4d39202c_392fcea4 
PS3, Line 216: AMD_ENABLE_MODERN_STANDBY
> this should also be a kconfig option (that i'd make default n) that adds the functionality when sele […]

I don't feel like I understand the benefit of separate S3/S0ix builds over a runtime setting. Also there is nothing preventing a mainboard author from setting this value with a Kconfig.