dt-bindings: iio: dac: ad5791: Add required voltage supplies

Vcc, iovcc, vrefp, and vrefn are needed for the DAC to work.
Add them as required bindings for ad5791.

Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Axel Haslam <ahaslam@baylibre.com>
Link: https://patch.msgid.link/20241031071746.848694-3-ahaslam@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/dac/adi,ad5791.yaml

@@ -26,6 +26,22 @@ properties:
   vdd-supply: true
   vss-supply: true
 
+  vcc-supply:
+    description:
+      Supply that powers the chip.
+
+  iovcc-supply:
+    description:
+      Supply for the digital interface.
+
+  vrefp-supply:
+    description:
+      Positive referance input voltage range. From 5v to (vdd - 2.5)
+
+  vrefn-supply:
+    description:
+      Negative referance input voltage range. From (vss + 2.5) to 0.
+
   adi,rbuf-gain2-en:
     description: Specify to allow an external amplifier to be connected in a
       gain of two configuration.
@@ -47,6 +63,10 @@ required:
   - reg
   - vdd-supply
   - vss-supply
+  - vcc-supply
+  - iovcc-supply
+  - vrefp-supply
+  - vrefn-supply
 
 allOf:
   - $ref: /schemas/spi/spi-peripheral-props.yaml#
@@ -65,6 +85,10 @@ examples:
             reg = <0>;
             vss-supply = <&dac_vss>;
             vdd-supply = <&dac_vdd>;
+            vcc-supply = <&dac_vcc>;
+            iovcc-supply = <&dac_iovcc>;
+            vrefp-supply = <&dac_vrefp>;
+            vrefn-supply = <&dac_vrefn>;
             reset-gpios = <&gpio_bd 16 GPIO_ACTIVE_LOW>;
             clear-gpios = <&gpio_bd 17 GPIO_ACTIVE_LOW>;
             ldac-gpios = <&gpio_bd 18 GPIO_ACTIVE_HIGH>;