Change in coreboot[master]: soc/intel/common: Add cpu_fill_code_cache() to test eNEM

[Arthur Heymans (Code Review)]

Attention is currently required from: Furquan Shaikh, Tim Wawrzynczak, Rizwan Qureshi, Subrata Banik, Patrick Rudolph, EricR Lai.
Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/55653 )

Change subject: soc/intel/common: Add cpu_fill_code_cache() to test eNEM
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Patch Set 3:

(1 comment)

Patchset:

PS3: 
How exactly does eNEM work?
Do you set up a CONFIG_DCACHE_RAM_SIZE region that never gets evicted and all the rest can be evicted if the cache is full? Or is specifically RO cached memory that gets evicted? If not you could set up a second WB region (just like the CAR one) large enough (larger than the cache) to ensure eviction and write to it. The address needs to be carefully selected though to not be a real address range. I'm not sure what happens when cache gets evicted to address that nothing is decoding. Anyway if that works, you could simplify this code a lot.