ARM: dts: raise GPU trip point temperature for speedy to 80 degC

Raise the temperature of the GPU thermal trip point for speedy
to 80°C. This is the value used by the downstream Chrome OS 3.14
kernel, the 'official' kernel for speedy.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>