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: <[e-mail]>
Fixes: 9843a2236003 ("ARM: dts: Provide dt bindings identical for Exynos TMU")
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>

arch/arm/boot/dts/exynos5250.dtsi

···
 &cpu_thermal {
 	polling-delay-passive = <0>;
 	polling-delay = <0>;
-	thermal-sensors = <&tmu 0>;
+	thermal-sensors = <&tmu>;
 
 	cooling-maps {
 		map0 {