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

[Ravindra (Code Review)]

Attention is currently required from: Furquan Shaikh, Maulik V Vaghela, Tim Wawrzynczak, Andrey Petrov, Patrick Rudolph.
Ravindra has uploaded a new patch set (#4) to the change originally created by Subrata Banik. ( 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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drivers/intel/fsp2_0: Allow `mp_startup_all_cpus()` to run serially

As per MP service specification, EDK2 is allowed to specify the mode
in which a 'func' routine would execute on APs as `SingleThread` sets
to 'true' meaning execute the function one by one (serially) or sets to
'false' meaning execute the function simultaneously.

MP service API `StartupAllAPs` has designed to pass such options as
part of function argument.

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.

BUG=b:199246420

Change-Id: Ia95d11408f663212fd40daa9fd9b0881a07f1ce7
Signed-off-by: Subrata Banik 
Signed-off-by: Ronak Kanabar 
---
M src/drivers/intel/fsp2_0/ppi/mp_service_ppi.c
1 file changed, 2 insertions(+), 3 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/43/57343/4