ARM: dts: stm32: remove fixed regulator unit address on stm32429i-eval

vref fixed regulator shouldn't have unit address and reg properties.
Rename the label and phandle to "vref" according to the schematics.
Also remove it from simple-bus.

Fixes: 7465d811 ("ARM: dts: stm32: enable ADC on stm32f429i-eval
board")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32429i-eval.dts

@@ -81,19 +81,13 @@ soc {
 		dma-ranges = <0xc0000000 0x0 0x10000000>;
 	};
 
-	regulators {
-		compatible = "simple-bus";
-		#address-cells = <1>;
-		#size-cells = <0>;
 
-		reg_vref: regulator@0 {
+	vref: regulator-vref {
 		compatible = "regulator-fixed";
-			reg = <0>;
 		regulator-name = "vref";
 		regulator-min-microvolt = <3300000>;
 		regulator-max-microvolt = <3300000>;
 	};
-	};
 
 	leds {
 		compatible = "gpio-leds";
@@ -157,7 +151,7 @@ mmc_vcard: mmc_vcard {
 &adc {
 	pinctrl-names = "default";
 	pinctrl-0 = <&adc3_in8_pin>;
-	vref-supply = <&reg_vref>;
+	vref-supply = <&vref>;
 	status = "okay";
 	adc3: adc@200 {
 		st,adc-channels = <8>;