Change in coreboot[master]: soc/intel: generate SSDT instead of using GNVS for SGX

[Nico Huber (Code Review)]

Attention is currently required from:  Felix Singer, Pratik Prajapati, Furquan Shaikh, Paul Menzel, Angel Pons, Subrata Banik, Michael Niewöhner, Andrey Petrov, Kyösti Mälkki, Patrick Rudolph, Pratikkumar V Prajapati.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/58394 )

Change subject: soc/intel: generate SSDT instead of using GNVS for SGX
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Patch Set 3:

(2 comments)

File src/soc/intel/common/block/sgx/sgx.c:

https://review.coreboot.org/c/coreboot/+/58394/comment/6806d814_40d2edea 
PS3, Line 273: }
Should this be in `acpi/acpi.c` like the other CPU/SSDT things?

File src/soc/intel/common/block/systemagent/systemagent.c:

PS3: 
Why system agent? Isn't it part of the CPU cores?