mickey crams a lot of hardware into a tiny package, which requires
more aggressive thermal throttling than for devices with a larger
footprint. Configure the GPU thermal zone to throttle the GPU
progressively at temperatures >= 60°C. Heat dissipated by the
CPUs also affects the GPU temperature, hence we cap the CPU
frequency to 1.4 GHz for temperatures above 65°C. Further throttling
of the CPUs may be performed by the CPU thermal zone.

The configuration matches that of the downstream Chrome OS 3.14
kernel, the 'official' kernel for mickey.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>