Change in coreboot[master]: supermicro/x11-lga1151-series: Remove SkipExtGfxScan = 1

[Nico Huber (Code Review)]

Attention is currently required from: Jan Tatje, Angel Pons, Michael Niewöhner.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/56071 )

Change subject: supermicro/x11-lga1151-series: Remove SkipExtGfxScan = 1
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Patch Set 3:

(1 comment)

Patchset:

PS2:
> FSP does this:
> ...

That's proves me right, doesn't it? i.e. for IVD, it only matters that
`PrimaryDisplay != (IGD, Auto)`.
> TL;DR IVD does not only depend on SkipExtGfxScan, but also on InternalGfx, PrimaryDisplay

I think you are reading it wrong. `PrimaryDisplay` is what matters most
for IVD: `IVD = PrimaryDisplay != IGD`. The other options just provide some
constraints for `PrimaryDisplay`, e.g. if not `SkipExtGfxScan` and something
is found, `Auto` is not turned into `IGD`; if not `InternalGfx`, `IGD` is not
an option for `PrimaryDisplay`.

I assume (no time to check right now), that the difference between `PCH_PCIe`
and `PEG` for `PrimaryDisplay` is only about bridge settings that coreboot
overwrites anyway. If that is the case, all that matters here is to set
`PrimaryDisplay != (Auto, IGD)`. If the options are too confusing, please
just test it.