arm64: dts: qcom: ipq6018: add usb3 DT description

Based on downstream codeaurora code.

Tested (USB2 only) on IPQ6010 based hardware.

Signed-off-by: Kathiravan T <kathirav@codeaurora.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
[bjorn: Changed dwc3 node name to usb, per binding]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/ebc2d340d566fa2d43127e253d5b8b134a87a78e.1630389452.git.baruch@tkos.co.il