dt-bindings: phy: qcom,qusb2: document sdm670 compatible

The Snapdragon 670 uses the QUSB driver for USB 2.0. Document the
compatible used in the device tree.
Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220922024656.178529-2-mailingradian@gmail.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/phy/qcom,qusb2-phy.yaml

@@ -30,6 +30,7 @@ properties:
       - items:
           - enum:
               - qcom,sc7180-qusb2-phy
+              - qcom,sdm670-qusb2-phy
               - qcom,sdm845-qusb2-phy
               - qcom,sm6350-qusb2-phy
           - const: qcom,qusb2-v2-phy