Change in coreboot[master]: cpu/x86/smm: Add smm_get_cbmemc_buffer for legacy SMI handler

[Raul Rangel (Code Review)]

Attention is currently required from: Arthur Heymans, Karthik Ramasubramanian.
Raul Rangel has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62793 )

Change subject: cpu/x86/smm: Add smm_get_cbmemc_buffer for legacy SMI handler
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Patch Set 2:

(1 comment)

Patchset:

PS2:
> I'd prefer not linking this code at buildtime instead of adding runtime failures.

We can tackle that one of two ways:
1) We can add `&& !CONFIG(LEGACY_SMP_INIT)` into [cbmem-console.c](https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/thir...)
2) We can add the same condition to https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/thir...

Both I would argue are a bit ugly. `LEGACY_SMP_INIT` is scheduled to be deleted. I would like to avoid adding `LEGACY_SMP_INIT` checks just to have someone clean them up later. Thoughts?