Change in coreboot[master]: drivers/intel/fsp2_0: Allow `mp_startup_all_cpus()` to run serially

[Tim Wawrzynczak (Code Review)]

Attention is currently required from: Furquan Shaikh, Subrata Banik, Ronak Kanabar, Andrey Petrov, Patrick Rudolph.
Tim Wawrzynczak has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/57343 )

Change subject: drivers/intel/fsp2_0: Allow `mp_startup_all_cpus()` to run serially
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Patch Set 1:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/57343/comment/48af61f2_dc480abb 
PS1, Line 17: But another MP service API `StartupAllCPUs` doesn't specifies any such
            : requirement. Running the `func` simultaneously on APs results into
            : coherency issue due to lack of acquire spin lock while accessing common
            : data structure in multiprocessor environment.
It's hard to figure out if this is called out explicitly anywhere... is this defined somewhere, or is this FSP behavior?

Is this causing any known issues?