atkbd: Flip the default for 'coreboot' to being normal

[imp]

Summary

This reverts commit 599a4548f8f1758afe1d33c53e9a56e42c5f3e30.
Revert "Adds support for Purism coreboot keyboards"

This reverts commit 07030f3362a75380f12fc82e68fba2b34ee2e32c.
Revert "atkbdc(4): Add quirk for "System76 lemur Pro" laptops."

This reverts commit 013da020e2c4974871caed321a29506582c73aed.
Revert "Assume all coreboot BIOSes have the need for these workarounds because"

Revert to only applying this quirk for really old Acer Peppy systems.
The dragonfly code that was ported over has since evolved to rearrange
the order of probing / resetting to better cope with this picky
system. However, ancient chromebooks are much less relevant today, so
default to no quirks for coreboot, except this specific ancient
chromebook. It turned out that my assuming all coreboot systems were
chromebook and needed the fix was in error and does hurt things now.

Add an UPDATING entry for people with different, but still old-enough to
need the quirk, chromebooks to contact me.

I'll note that Dragonfly has reworked the atkbd/atkbdc probing code so
many of these quirks (all?) are no longer necessary. That's beyond the
scope of what I have time for, but would make a good project for
someone, perhaps in combination of eliminating GIANT in the kbd/mouse
subsystem.

Relnotes: yes
Sponsored by: Netflix

Test Plan

Also seeing if I can find a way to see if there's a generic way to detect the old, broken code with the coreboot folks.

[rpokala]

I don't have any particular context for this issue, but the description makes sense, and the code change implements it.

[imp]

This is too flawed. Found a better way in D40789.