ARM: dts: exynos: Document regulator used by ADC on Odroid U3

Add ADC node to Odroid U3 with its regulator, purely for documentation
purposes.  The ADC stays disabled because it is not used (all inputs
grounded).
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

arch/arm/boot/dts/exynos4412-odroidu3.dts

@@ -66,6 +66,11 @@ map2 {
 	};
 };
 
+&adc {
+	vdd-supply = <&ldo10_reg>;
+	/* Nothing connected to ADC inputs, keep it disabled */
+};
+
 /* Supply for LAN9730/SMSC95xx */
 &buck8_reg {
 	regulator-name = "BUCK8_P3V3";