Change in coreboot[master]: mb/google/nissa/var/nivviks: Add GL9750 power sequence

[Kangheui Won (Code Review)]

Attention is currently required from: Tim Wawrzynczak, Reka Norman, Eric Lai.
Kangheui Won has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62722 )

Change subject: mb/google/nissa/var/nivviks: Add GL9750 power sequence
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Patch Set 1:

(1 comment)

File src/mainboard/google/brya/variants/nivviks/gpio.c:

https://review.coreboot.org/c/coreboot/+/62722/comment/ee1f707a_696e61d8 
PS1, Line 56: PAD_CFG_GPO(GPP_H12, 1, DEEP)
> If you check brya variants again, you will see several of them have moved deassertoin of PERST_L for […]

Not objecting to moving to ramstage if it works, but I also think romstage would be safer choice in case it takes a while after PERST to respond to PCIe scanning.