Change in coreboot[master]: apple/macbook21: configure the clockgen and add C3 CPU state

[Ferass EL HAFIDI (Code Review)]

Attention is currently required from: Ferass EL HAFIDI, Paul Menzel, Arthur Heymans, Evgeny Zinoviev, Felix Held.
Hello build bot (Jenkins), Nico Huber, Arthur Heymans, Evgeny Zinoviev, Felix Held,

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

https://review.coreboot.org/c/coreboot/+/63587

to look at the new patch set (#7).

Change subject: apple/macbook21: configure the clockgen and add C3 CPU state
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apple/macbook21: configure the clockgen and add C3 CPU state

To add the C3 CPU state, the clockgen has to be reconfigured.
The values are taken from the MacBook's vendor firmware
with i2cdump.
The overridetree is used here because this patch is currently
untested on iMac5,2 computers and I'm not sure if the values
in it are the same as in the iMac5,2. The iMac5,2 uses
CY285566 while the MacBook2,1 uses SLG8LP436 so to prevent
coreboot from setting up a possible wrong configuration, I
prefer using a separate `overridetree.cb`. I also put C3 in
`cstates.c` between `#if !CONFIG(BOARD_APPLE_IMAC52)` and
`#endif` to prevent the iMac5,2 from using C3 or else ACPI
will be basically broken.

Change-Id: Ib97f95599fbdf66aa55e936bdcb9cc0cd69b3824
Signed-off-by: Ferass 'Vitali64' EL HAFIDI 
---
M src/mainboard/apple/macbook21/Kconfig
M src/mainboard/apple/macbook21/cstates.c
A src/mainboard/apple/macbook21/variants/macbook21/overridetree.cb
3 files changed, 32 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/87/63587/7