Change in coreboot[master]: src/soc/intel/*: Change legacy_8254_timer to CMOS option

[Angel Pons (Code Review)]

Attention is currently required from: Sean Rhodes, Jeremy Soller, Tim Wawrzynczak, Patrick Rudolph.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/56256 )

Change subject: src/soc/intel/*: Change legacy_8254_timer to CMOS option
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Patch Set 4: Code-Review-1

(3 comments)

Patchset:

PS4: 
Please don't make this setting *only* configurable via CMOS. Making this setting configurable using either Kconfig or CMOS is possible and simpler to implement (see comment in soc/intel/skylake code).

File src/mainboard/hp/280_g2/cmos.default:

https://review.coreboot.org/c/coreboot/+/56256/comment/ed5d580b_fa21bfd9 
PS4, Line 1: legacy_8254_timer=Disable
Why `Disable`? The default for this board is to enable 8254. Moreover, this file and cmos.layout are dead: one can't use them if HAVE_CMOS_DEFAULT and HAVE_OPTION_TABLE are not selected.

I'm against making this option *only* configurable via CMOS. I've suggested an approach in a comment on soc/intel/skylake code that does not require touching any mainboards.

File src/soc/intel/skylake/chip.c:

https://review.coreboot.org/c/coreboot/+/56256/comment/444c9f53_c96d6561 
PS4, Line 346: 1
If you leave the Kconfig option as-is and use `CONFIG(USE_LEGACY_8254_TIMER)` as the argument for `fallback`, you don't need to touch any mainboards.

const bool legacy_8254_timer = get_uint_option("legacy_8254_timer", CONFIG(USE_LEGACY_8254_TIMER));