dt-bindings: iio: addac: adi,one-bit-adc-dac: fix tabs instead of spaces

The adi,one-bit-adc-dac.yaml file had tabs instead of spaces at the end
which caused `make dt_binding_check` to skip the file with the following
warning:

    /home/david/work/linux/Documentation/devicetree/bindings/iio/addac/adi,one-bit-adc-dac.yaml: ignoring, error parsing file

Fixes: e36fa74 ("dt-binding: iio: Add documentation for one_bit_adc_dac")
Signed-off-by: David Lechner <dlechner@baylibre.com>

Author: dlech

Documentation/devicetree/bindings/iio/addac/adi,one-bit-adc-dac.yaml

@@ -83,5 +83,5 @@ examples:
           reg = <3>;
           label = "o_24";
         };
-			};
-		};
+      };
+    };