dt-bindings: iio: adc: ad7192: Add aincom supply

AINCOM should actually be a supply. AINx inputs are referenced to AINCOM
in pseudo-differential operation mode. AINCOM voltage represents the
offset of corresponding channels.
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Alisa-Dariana Roman <alisa.roman@analog.com>
Link: https://lore.kernel.org/r/20240514120222.56488-3-alisa.roman@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/adi,ad7192.yaml

@@ -41,6 +41,11 @@ properties:
   interrupts:
     maxItems: 1
 
+  aincom-supply:
+    description: |
+      AINCOM voltage supply. Analog inputs AINx are referenced to this input
+      when configured for pseudo-differential operation.
+
   dvdd-supply:
     description: DVdd voltage supply
 
@@ -117,6 +122,7 @@ examples:
             clock-names = "mclk";
             interrupts = <25 0x2>;
             interrupt-parent = <&gpio>;
+            aincom-supply = <&aincom>;
             dvdd-supply = <&dvdd>;
             avdd-supply = <&avdd>;
             vref-supply = <&vref>;