arm64: dts: meson-gxbb-wetek: enable SARADC

Enable SARADC on Wetek Boards.
Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm64/boot/dts/amlogic/meson-gxbb-wetek.dtsi

@@ -59,6 +59,13 @@ vddao_3v3: regulator-vddao_3v3 {
 		regulator-max-microvolt = <3300000>;
 	};
 
+	vddio_ao18: regulator-vddio_ao18 {
+		compatible = "regulator-fixed";
+		regulator-name = "VDDIO_AO18";
+		regulator-min-microvolt = <1800000>;
+		regulator-max-microvolt = <1800000>;
+	};
+
 	vcc_3v3: regulator-vcc_3v3 {
 		compatible = "regulator-fixed";
 		regulator-name = "VCC_3V3";
@@ -172,6 +179,11 @@ &pwm_ef {
 	clock-names = "clkin0";
 };
 
+&saradc {
+	status = "okay";
+	vref-supply = <&vddio_ao18>;
+};
+
 /* Wireless SDIO Module */
 &sd_emmc_a {
 	status = "okay";