Change in coreboot[master]: soc/intel/alderlake: Refactor MultiPhaseSiInit API calling method

[Angel Pons (Code Review)]

Attention is currently required from: Furquan Shaikh, Tim Wawrzynczak, Paul Menzel, Subrata Banik, Patrick Rudolph, EricR Lai.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/56382 )

Change subject: soc/intel/alderlake: Refactor MultiPhaseSiInit API calling method
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Patch Set 9:

(1 comment)

File src/drivers/intel/fsp2_0/silicon_init.c:

https://review.coreboot.org/c/coreboot/+/56382/comment/07d61178_8f66a06e 
PS8, Line 80: #endif
> > Right, so TGL has an UPD to enable multi-phase Si init, but it's not in the FSPS_ARCH_UPD... […]

The problem with using a __weak definition for `enable_multi_phase_init()` is that it doesn't do anything when CONFIG_FSPS_HAS_ARCH_UPD=n and SoC doesn't provide an override. In this case, it's possible to call FSP-S without setting `EnableMultiPhaseSiliconInit` even when CONFIG_FSPS_USE_MULTI_PHASE_INIT=y, which can cause issues.

By guarding the entire function definition and not using __weak, SoCs with CONFIG_FSPS_USE_MULTI_PHASE_INIT=y and CONFIG_FSPS_HAS_ARCH_UPD=n are required to define `enable_multi_phase_init()`. Otherwise, building fails.