[S] Change in coreboot[main]: mb/google/rex/var/rex: Configure PL4 to 64W if battery status is invalid

[Caveh Jalali (Code Review)]

Attention is currently required from: Brandon Breitenstein, Eran Mitrani, Hannah Williams, Jamie Ryu, Kapil Porwal, Subrata Banik, Sukumar Ghorai, Tarun.

Caveh Jalali has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78322?usp=email )

Change subject: mb/google/rex/var/rex: Configure PL4 to 64W if battery status is invalid
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Patch Set 5:

(2 comments)

File src/mainboard/google/rex/variants/baseboard/rex/ramstage.c:

https://review.coreboot.org/c/coreboot/+/78322/comment/181cb4e6_333fe89c :
PS5, Line 25: p
> Acknowledged

'optimized' sounds like the preferred/nominal profile,
but this is really the fail-safe profile.

https://review.coreboot.org/c/coreboot/+/78322/comment/b01d8331_3d560df4 :
PS5, Line 48: battery_status
> What is the condition we are going to check to limit PL4 now? Are we going to consider Battery level […]

`EC_BATT_FLAG_LEVEL_CRITICAL` means we're below
`CONFIG_BATT_HOST_SHUTDOWN_PERCENTAGE` (default 4%)
at which point we notify the AP with `EC_HOST_EVENT_BATTERY_CRITICAL`
in the hopes the user is notified before we force a shutdown
or things go dark.

there are a bunch of additional thresholds that go into deciding
to shut down the AP...