[M] Change in coreboot[master]: mb/google/hatch: Kohaku - ensure FPMCU is power cycled on reset

[Tarun Tuli (Code Review)]

Attention is currently required from: Eran Mitrani, Nick Vaccaro.

Hello Shelley Chen, build bot (Jenkins), Eran Mitrani, Nick Vaccaro,

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

https://review.coreboot.org/c/coreboot/+/68819

to look at the new patch set (#20).

Change subject: mb/google/hatch: Kohaku - ensure FPMCU is power cycled on reset
......................................................................

mb/google/hatch: Kohaku - ensure FPMCU is power cycled on reset

Leakage from the SPI CS line onto the FPMCU VDD rail was preventing
the FPMCU from fully shutting down on AP reset.

Instead of simply turning off the power rail, now ensure the CS
line is not driven high until late in coreboot.

This ensures it is completely off for the requisite minimum of 200ms
(now measured at approx 1100ms).

BUG=b:245953688
TEST=Confirmed FPMCU is still functional on Kohaku.
Confirmed FpRebootPowerCycle unit test now passes
BRANCH=Hatch

Signed-off-by: Tarun Tuli 
Change-Id: I1e7e32f61c3ac1b3154d42821cc1dd4c5d3de303
---
M src/mainboard/google/hatch/variants/kohaku/gpio.c
M src/mainboard/google/hatch/variants/kohaku/ramstage.c
2 files changed, 50 insertions(+), 3 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/19/68819/20