Change in coreboot[master]: mb/google/brya/var/agah: Add GPU power sequencing

[Tim Wawrzynczak (Code Review)]

Attention is currently required from: Tim Wawrzynczak, Nick Vaccaro.
Hello build bot (Jenkins), Subrata Banik, Angel Pons, Nick Vaccaro,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/62384

to look at the new patch set (#4).

Change subject: mb/google/brya/var/agah: Add GPU power sequencing
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mb/google/brya/var/agah: Add GPU power sequencing

This patch adds support for power sequencing of the Nvidia GN3050 for
agah, which uses PCH GPIOs to control the 5 power rails required for
the GPU. The GPU is power sequenced on during mainboard
initialization, then it is enumerated on the PCI bus and its resources
are assigned. This GPU will be used in a sort of "hybrid graphics"
mode, therefore during finalization, since its PCI BARs are saved into
ACPI memory and the GPU is not required upon initial boot, the GPU is
power sequenced off.

Signed-off-by: Tim Wawrzynczak 
Change-Id: I1072be12ef58af5859e2a2d19c4a9c1adc0b0f88
---
M src/mainboard/google/brya/variants/agah/Makefile.inc
M src/mainboard/google/brya/variants/agah/overridetree.cb
A src/mainboard/google/brya/variants/agah/variant.c
3 files changed, 194 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/84/62384/4