[M] Change in coreboot[main]: soc/intel/cmn/gfx: Fix GFX modeset issue with dual-display

[Nico Huber (Code Review)]

Attention is currently required from: Eric Lai, Kapil Porwal, Nick Vaccaro, Paz Zcharya, Subrata Banik.

Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78691?usp=email )

Change subject: soc/intel/cmn/gfx: Fix GFX modeset issue with dual-display
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Patch Set 4:

(1 comment)

Patchset:

PS4: 
Sorry, I missed all the MBUS reviews. This looks like workarounds for using
the FSP/GOP as it would otherwise be implemented as part of the gfx init.
Have you considered to implement this in `drivers/intel/fsp/`?

The logic in get_external_display_status() looks suspiciously as it would
only work for the default pipe allocation chosen by the GOP. The internal
display is often but not always on PORT_A. And PORT_A can also be used with
any pipe (i.e. not always pipe A). If the intend is to only make it work
with the GOP, please move the code.