ARM: dts: exynos: Only Odroid XU3-family boards use DTSI with CPU thermal nodes

Include the CPU thermal nodes directly in Odroid XU3-family common DTS
because it is the only user of it. Keeping it in separate DTSI file does
not bring benefits because:
1. It is not re-usable on other non-fan boards (fan is referenced),
2. It won't be re-used on future Odroid XU board because different
   CPU cluster behavior.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Tested-by: Anand Moon <linux.amoon@gmail.com>