dt-bindings: iio: light: vishay,veml6075: make vdd-supply required

The VEML6075 requires a single supply to operate. The property already
exists in the bindings and it is used in the example, but it is still
not on the list of required properties.
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240223-veml6075_vdd-v1-1-ac76509b1998@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml

@@ -21,6 +21,7 @@ properties:
 required:
   - compatible
   - reg
+  - vdd-supply
 
 additionalProperties: false