ARM: dts: exynos: Add CPU cooling in SMDKv310

Add missing cooling devices for CPU thermal zones in Exynos4210 SMDKv310
board.  This allows to scale down CPU frequency (and voltage) in case of
thermal pressure.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200830135200.24304-20-krzk@kernel.org