dt-bindings: usb: dwc2: add optional usb-role-switch property

This patch documents the usb-role-switch property in dwc2 bindings, now
that usb-role-switch support is available in dwc2 driver.
Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

Documentation/devicetree/bindings/usb/dwc2.yaml

@@ -103,6 +103,10 @@ properties:
   dr_mode:
     enum: [host, peripheral, otg]
 
+  usb-role-switch:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description: Support role switch.
+
   g-rx-fifo-size:
     $ref: /schemas/types.yaml#/definitions/uint32
     description: size of rx fifo size in gadget mode.