[M] Change in libgfxinit[master]: gma: Update DP training with new fields

[Nico Huber (Code Review)]

Attention is currently required from: Angel Pons, Arthur Heymans, Jérémy Compostella, Tim Wawrzynczak.

Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/libgfxinit/+/67490?usp=email )

Change subject: gma: Update DP training with new fields
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Patch Set 18:

(1 comment)

File common/hw-gfx-dp_training.ads:

https://review.coreboot.org/c/libgfxinit/+/67490/comment/7681f49e_73356e2f :
PS8, Line 23:    type T (<>) is limited private;
> That could work, more like a `Port_Info` for TGL+ anyways; I was disappointed I had to go back and c […]

I was able to boil it down to the addition of `Port_Config.Is_eDP` and
this patch to CB:67499: http://ix.io/4xm5

Didn't push a new patch set because I don't want to make the queue
more confusing. Maybe we should just skip it for now until we get to
CB:67499. WDYT?