[S] Change in coreboot[main]: drivers/intel/fsp2_0/ppi: Fix FSP PPI callback calling convention

[Subrata Banik (Code Review)]

Attention is currently required from: Andrey Petrov, Arthur Heymans, Chen, Gang C, Jincheng Li, Jérémy Compostella, Ronak Kanabar, Shuo Liu.

Subrata Banik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/80574?usp=email )

Change subject: drivers/intel/fsp2_0/ppi: Fix FSP PPI callback calling convention
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Patch Set 7:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/80574/comment/3833c31a_173a00c8 :
PS7, Line 9: Multi Processor PEIM-to-PEIM Interface deals with pointer to function
           : living in FSP space 
this is not correct, with a unified stack between FSP and coreboot. This code is getting executed in the context of coreboot rather than FSP.

i would like to understand the problem in detail about what you are running into. So far, we are using this PPI for many platforms and don't see any problem.