mainboards: Remove unused EC event for thermal overload

The Chrome EC event for "thermal overload" was never implemented and
is being repurposed as the EC event mask is out of free bits.

Remove this from the boards that were enabling it.

BUG=b:36024430
TEST=build coreboot for affected boards

Change-Id: I6038389ad73cef8a57aec5041bbb9dea98ed2b6e
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/20424
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
16 files changed