[S] Change in coreboot[main]: ext_stage_cache: Make sure variables are initialized

[Nico Huber (Code Review)]

Attention is currently required from: Angel Pons, Arthur Heymans, Jérémy Compostella.

Nico Huber has posted comments on this change by Arthur Heymans. ( https://review.coreboot.org/c/coreboot/+/84040?usp=email )

Change subject: ext_stage_cache: Make sure variables are initialized
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Patch Set 7: Code-Review+1

(2 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/84040/comment/9dca9c8b_655e226d?usp... :
PS7, Line 10: 
Maybe add: `Also exit gracefully from stage-cache code if no smm region is found.`
Actually, I'd prefer if we can solve this puzzle semantically, though. i.e.
make sure `smm_subregion(SMM_SUBREGION_CACHE, ...` can't fail.

File src/cpu/x86/smm/tseg_region.c:

https://review.coreboot.org/c/coreboot/+/84040/comment/0cbed9da_f34c5768?usp... :
PS7, Line 34: 		return -1;
Hmmm, do we ever link this path? Because here start/size would
indeed have been uninitialized.

If not we could put `dead_code();` here.