dt-bindings: iio: resolver: adi,ad2s90: use spi-peripheral-props.yaml

For devices connectable by SPI bus (e.g. already using
"spi-max-frequency" property), reference the "spi-peripheral-props.yaml"
schema to allow using all SPI device properties, 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/20221004115642.63749-8-krzysztof.kozlowski@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/resolver/adi,ad2s90.yaml

@@ -33,8 +33,6 @@ properties:
 
   spi-cpha: true
 
-additionalProperties: false
-
 required:
   - compatible
   - reg
@@ -43,6 +41,11 @@ dependencies:
   spi-cpol: [ spi-cpha ]
   spi-cpha: [ spi-cpol ]
 
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
 examples:
   - |
     spi {