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

[Michael Niewöhner (Code Review)]

Attention is currently required from: Nico Huber, Jan Tatje.
Michael Niewöhner 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:
> Everything else (wrt. PrimaryDisplay) can be handled without FSP.

I doubt it, since there's too much dependencies between various graphics UPDs and possible configurations (IGD fused, unfused, PEG present or nor, PCIe present or not, all three or just two or one, VGA jumper set or unset and all combinations of these). The "fastest solution" would be just using the UPDs (even though, I don't like to rely on FSP, too).

FSP does this:

```
set IVD=1 (pre-mem)

Switchable graphics init (GPIOs, timing, subsystem ids, and some other stuff)

if SkipExtGfxScan == 0
  Check for PCIe VGA
  Check for PEG VGA and configure it

if IGD not supported e.g. fused (IGD_VID == 0xFFFF) || InternalGfx == 0
  IVD = 1
  Disable IGD

if InternalGfx == 1 || (PrimaryDisplay == IGD && InternalGfx != 0)  # IGfx can be 2 internally o.O
  if PrimaryDisplay == IGD
    IVD = 0
  else
    IVD = 1
```

TL;DR IVD does not only depend on SkipExtGfxScan, but also on InternalGfx, PrimaryDisplay

side note: IGD can be enabled with unfused cpus/socs to use it for graphics computing, even without output ports. That's why we don't disable it.