arm64: dts: imx8mm-evk: Describe the OV5640 supplies

Per ovti,ov5640.yaml, the OV5640 power supplies are mandatory
properties.

Describe them to fix dt-schema warnings.
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-evk.dtsi

@@ -72,6 +72,20 @@ reg_usdhc2_vmmc: regulator-usdhc2 {
 		enable-active-high;
 	};
 
+	reg_1v5: regulator-1v5 {
+		compatible = "regulator-fixed";
+		regulator-name = "VDD_1V5";
+		regulator-min-microvolt = <1500000>;
+		regulator-max-microvolt = <1500000>;
+	};
+
+	reg_1v8: regulator-1v8 {
+		compatible = "regulator-fixed";
+		regulator-name = "VDD_1V8";
+		regulator-min-microvolt = <1800000>;
+		regulator-max-microvolt = <1800000>;
+	};
+
 	reg_vddext_3v3: regulator-vddext-3v3 {
 		compatible = "regulator-fixed";
 		regulator-name = "VDDEXT_3V3";
@@ -441,6 +455,9 @@ camera@3c {
 		assigned-clock-rates = <24000000>;
 		powerdown-gpios = <&gpio1 7 GPIO_ACTIVE_HIGH>;
 		reset-gpios = <&gpio1 6 GPIO_ACTIVE_LOW>;
+		DOVDD-supply = <&buck5_reg>;
+		AVDD-supply = <&reg_1v8>;
+		DVDD-supply = <&reg_1v5>;
 
 		port {
 			ov5640_to_mipi_csi2: endpoint {