dt-bindings: usb: qcom,dwc3: Add compatible for SC7180

Add compatible for SC7180 in usb dwc3 bindings.

Signed-off-by: Sandeep Maheswaram <sanm@codeaurora.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Rob Herring <robh@kernel.org>