dt-bindings: power: supply: bq24190: use regulator schema for child node

The 'usb-otg-vbus' child node is a regulator so reference the regulator
schema for proper evaluation.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/devicetree/bindings/power/supply/bq24190.yaml

@@ -28,7 +28,7 @@ properties:
     maxItems: 1
 
   usb-otg-vbus:
-    type: object
+    $ref: /schemas/regulator/regulator.yaml#
     description: |
       Regulator that is used to control the VBUS voltage direction for
       either USB host mode or for charging on the OTG port