ARM: dts: exynos: correct TMU phandle in Exynos5250

TMU node uses 0 as thermal-sensor-cells, thus thermal zone referencing
it must not have an argument to phandle.

Cc: <stable@vger.kernel.org>
Fixes: 9843a223 ("ARM: dts: Provide dt bindings identical for Exynos TMU")
Link: https://lore.kernel.org/r/20230209105841.779596-3-krzysztof.kozlowski@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>