dt-bindings: iio: addac: adi,ad74413r: use spi-peripheral-props.yaml

Reference the spi-peripheral-props.yaml schema to allow using all
properties typical for SPI-connected devices, even these which device
bindings author did not tried yet.

While changing additionalProperties->unevaluatedProperties, put it in
typical place, just before example DTS.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221004115642.63749-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/addac/adi,ad74413r.yaml

@@ -58,8 +58,6 @@ required:
   - spi-cpol
   - refin-supply
 
-additionalProperties: false
-
 patternProperties:
   "^channel@[0-3]$":
     type: object
@@ -103,6 +101,11 @@ patternProperties:
     required:
       - reg
 
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
 examples:
   - |
     #include <dt-bindings/gpio/gpio.h>