dt-bindings: usb: qcom,dwc3: allow required-opps

Few Qualcomm SoCs require minimum performance level of power domain, so
allow it:

  sm8550-mtp.dtb: usb@a6f8800: 'required-opps' does not match any of the regexes: '^usb@[0-9a-f]+$', 'pinctrl-[0-9]+'
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230127121122.342191-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/qcom,dwc3.yaml

@@ -58,6 +58,9 @@ properties:
     description: specifies a phandle to PM domain provider node
     maxItems: 1
 
+  required-opps:
+    maxItems: 1
+
   clocks:
     description: |
       Several clocks are used, depending on the variant. Typical ones are::