dt-bindings: usb: usb-nop-xceiv: add wakeup-source property

USB phy may be a system wakeup source, so add wakeup source property
to keep its resource (e.g. power domain) active to make USB remote
wakeup work.
Signed-off-by: Li Jun <jun.li@nxp.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/1666764742-4201-1-git-send-email-jun.li@nxp.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/usb-nop-xceiv.yaml

@@ -39,6 +39,11 @@ properties:
       the VBus line.
     $ref: /schemas/types.yaml#/definitions/phandle
 
+  wakeup-source:
+    description:
+      Specify if the USB phy can detect the remote wakeup signal
+      while the system sleep.
+
 required:
   - compatible
   - '#phy-cells'