dt-bindings: phy: qcom-qusb2: Document SDM660 compatible

Support for the SDM630/660 series of SoCs was added to the driver:
document the qcom,sdm660-qusb2-phy compatible here.
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210114174718.398638-3-angelogioacchino.delregno@somainline.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

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

@@ -21,6 +21,7 @@ properties:
               - qcom,ipq8074-qusb2-phy
               - qcom,msm8996-qusb2-phy
               - qcom,msm8998-qusb2-phy
+              - qcom,sdm660-qusb2-phy
       - items:
           - enum:
               - qcom,sc7180-qusb2-phy