dt-bindings: power: supply: summit,smb347: use absolute path to schema

Reference regulator schema by absolute path, as expected by DT schema
coding style.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: David Heidelberg <david@ixit.cz>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/devicetree/bindings/power/supply/summit,smb347-charger.yaml

@@ -82,7 +82,7 @@ properties:
       - 1 # SMB3XX_SYSOK_INOK_ACTIVE_HIGH
 
   usb-vbus:
-    $ref: "../../regulator/regulator.yaml#"
+    $ref: /schemas/regulator/regulator.yaml#
     type: object
 
     properties: