dt-bindings: iio: adc: ad4851: add spi-3wire

Add devicetree support for spi 3-wire configuration.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250626104024.8645-1-antoniu.miclaus@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: amiclaus

Documentation/devicetree/bindings/iio/adc/adi,ad4851.yaml

@@ -69,6 +69,8 @@ properties:
   spi-max-frequency:
     maximum: 25000000
 
+  spi-3wire: true
+
   '#address-cells':
     const: 1