dt-bindings: iio/dac: adi,ad5766: Add missing type to 'output-range-microvolts'

'output-range-microvolts' is missing a type definition. '-microvolts' is not a standard unit (should be '-microvolt'). As the property is already in use, add a type reference.

---
 Documentation/devicetree/bindings/iio/dac/adi,ad5766.yaml | 2 ++
 1 file changed, 2 insertions(+)

index a8f7720d1e3e..29bd16dab546 100644
@@ -22,6 +22,8 @@ properties:
       - adi,ad5767
 
   output-range-microvolts:
+    $ref: /schemas/types.yaml#/definitions/int32-array
+    maxItems: 2
     description: Select converter output range.
 
   reg:

2.34.1

Applied, thanks!