Change in coreboot[master]: soc/intel/cmn/spi: Add ACPI SSDT extension for fast SPI

[Arthur Heymans (Code Review)]

Attention is currently required from: Nico Huber, Subrata Banik, Paul Menzel, Werner Zeh.
Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/63982 )

Change subject: soc/intel/cmn/spi: Add ACPI SSDT extension for fast SPI
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Patch Set 2:

(1 comment)

File src/soc/intel/common/block/spi/spi.c:

https://review.coreboot.org/c/coreboot/+/63982/comment/02fbdd02_9d0e7ea6 
PS1, Line 117: spi_fill_ssdt
> The `hidden` keyword is a hack for devices that are hidden from coreboot.
> So `dev->hidden` is actually reliable, it has to be. But it serves a different
> purpose.

Would it make sense to just do a basic check: only add ACPI code for B:D:F if B:D:0 is not discoverable to the OS (be it hidden or disabled)?