[M] Change in coreboot[main]: soc/intel/alderlake: Add a function to force disable memory channels

[Angel Pons (Code Review)]

Attention is currently required from: Christian Walter, Dinesh Gehlot, Jayvik Desai, Jeremy Soller, Kapil Porwal, Lean Sheng Tan, Michał Kopeć, Michał Żygowski, Nick Vaccaro, Piotr Król, Sean Rhodes, Tim Crawford.

Angel Pons has posted comments on this change by Kapil Porwal. ( https://review.coreboot.org/c/coreboot/+/85529?usp=email )

Change subject: soc/intel/alderlake: Add a function to force disable memory channels
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Patch Set 1:

(2 comments)

File src/soc/intel/alderlake/meminit.c:

https://review.coreboot.org/c/coreboot/+/85529/comment/24d8bf62_380c3a51?usp... :
PS1, Line 264: void memcfg_init(FSPM_UPD *memupd, const struct mb_cfg *mb_cfg,
             : 		 const struct mem_spd *spd_info, bool half_populated,
             : 		 uint32_t ch_disable_mask)
> wondering if you really need to change the API to accommodate `ch_disable_mask`. […]

How about:

```suggestion
void memcfg_init(FSPM_UPD *memupd, const struct mb_cfg *mb_cfg,
    	 const struct mem_spd *spd_info, bool half_populated){
    memcfg_init_with_ch_mask(memupd, mb_cfg, spd_info, half_populated, 0);
}

void memcfg_init_with_ch_mask(FSPM_UPD *memupd, const struct mb_cfg *mb_cfg,
    	 const struct mem_spd *spd_info, bool half_populated,
    	 uint32_t ch_disable_mask)
```

This way, there's no need to touch every mainboard using `memcfg_init`. I know it's not the prettiest approach, but C doesn't allow specifying default values for parameters.

https://review.coreboot.org/c/coreboot/+/85529/comment/e4a4202a_038c5d1c?usp... :
PS1, Line 315: 	mem_init_override_channel_mask(mem_cfg, ch_disable_mask);
Could this be called at the very end of the function? If so, you could export this function (make it non-static) and call it from mainboards.