dt-bindings: gpio: fairchild,74hc595: use spi-peripheral-props.yaml

Instead of listing directly properties typical for SPI peripherals,
reference the spi-peripheral-props.yaml schema.  This allows using all
properties typical for SPI-connected devices, even these which device
bindings author did not tried yet.

Remove the spi-* properties which now come via spi-peripheral-props.yaml
schema, except for the cases when device schema adds some constraints
like maximum frequency.

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>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Documentation/devicetree/bindings/gpio/fairchild,74hc595.yaml

@@ -33,8 +33,6 @@ properties:
     description: GPIO connected to the OE (Output Enable) pin.
     maxItems: 1
 
-  spi-max-frequency: true
-
 patternProperties:
   "^(hog-[0-9]+|.+-hog(-[0-9]+)?)$":
     type: object
@@ -59,7 +57,10 @@ required:
   - '#gpio-cells'
   - registers-number
 
-additionalProperties: false
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
 
 examples:
   - |