arm64: dts: rockchip: move the rk3368 thermal data into rk3368.dtsi

In order to be standard to manage for rockchip SoCs,  move the thermal
data into rk3368 dtsi, we needn't to add a new file for thermal.

Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>