dt-bindings: iio: semtech,sx9310: reference common schema for label

Reference iio.yaml schema from dtschema to allow already used
label property:

  sc7180-trogdor-homestar-r4.dtb: proximity@28: 'label' does not match any of the regexes: 'pinctrl-[0-9]+'
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230617103658.114453-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/proximity/semtech,sx9310.yaml

@@ -15,6 +15,9 @@ description: |
   Specifications about the devices can be found at:
   https://www.semtech.com/products/smart-sensing/sar-sensors/sx9310
 
+allOf:
+  - $ref: /schemas/iio/iio.yaml#
+
 properties:
   compatible:
     enum:
@@ -102,7 +105,7 @@ required:
   - reg
   - "#io-channel-cells"
 
-additionalProperties: false
+unevaluatedProperties: false
 
 examples:
   - |