dt-bindings: iio: adc: adi,ad7292: Fix additionalProperties on channel nodes

"additionalProperties: true" is only for incomplete schemas such as bus
child nodes in a bus's schema. That doesn't apply to the "channel" nodes
in the adi,ad7292 binding, so fix additionalProperties to be false.
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Link: https://lore.kernel.org/r/20230926164357.100325-1-robh@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/adi,ad7292.yaml

@@ -61,7 +61,7 @@ patternProperties:
     required:
       - reg
 
-    additionalProperties: true
+    additionalProperties: false
 
 allOf:
   - $ref: /schemas/spi/spi-peripheral-props.yaml#