dt-bindings: usb: qcom,dwc3: add binding for IPQ6018

Add compatible string for Qualcomm IPQ6018 SoC.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Link: https://lore.kernel.org/r/6a9b00d16a707aa2a94bcba71a24932cc201a473.1630389452.git.baruch@tkos.co.il


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>