dt-bindings: backlight: kinetic,ktz8866: Add missing type for "current-num-sinks"

"current-num-sinks" is missing a type, add it.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230613201022.2823392-1-robh@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>

Author: robherring

Documentation/devicetree/bindings/leds/backlight/kinetic,ktz8866.yaml

@@ -33,6 +33,7 @@ properties:
 
   current-num-sinks:
     description: number of the LED current sinks' channels.
+    $ref: /schemas/types.yaml#/definitions/uint32
     enum: [1, 2, 3, 4, 5, 6]
 
   kinetic,current-ramp-delay-ms: