dt-bindings: usb: dwc2: add support for APM82181 SoCs USB OTG HS and FS

adds the specific compatible string for the DWC2 IP found in the APM82181
SoCs. The APM82181's USB-OTG seems like it was taken from its direct
predecessor: the PPC460EX (canyonlands).
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

Documentation/devicetree/bindings/usb/dwc2.yaml

@@ -39,6 +39,7 @@ properties:
               - amlogic,meson-g12a-usb
           - const: snps,dwc2
       - const: amcc,dwc-otg
+      - const: apm,apm82181-dwc-otg
       - const: snps,dwc2
       - const: st,stm32f4x9-fsotg
       - const: st,stm32f4x9-hsotg