atkbc: Better test for old chromebooks

Older Chromebooks have issues in their embedded controller (EC) firmware
which need working around in atkbd and atkbdc. On these systems, rather
than use a standard EC, Google used their own arm-based EC. For a while,
its firmware incorrectly implemented the i8042, requiring workaroundsd
in the driver.

Implement a heuristic recommended by MrChromebox <mrchromebox@gmail.com>
to detect them: If the bios.version starts with Google_, or the maker is
either Google or GOOGLE, assume that it's a chromebook with the affected
bios. While this isn't strictly true, the number of updated systems
without the bug is very small and this will exclude all the non-Google
coreboot user that use a standard EC. There's no simple way to test the
hardware to see if it's implemented with the buggy EC.

Sponsored by: Netflix
Reviewed by: jon@thesoo.org, MrChromebox
Differential Revision: https://reviews.freebsd.org/D40789