arm64: dts: msm8996: Add device node for qcom,dwc3

Adding required device node for couple of DWC3 controllers
present on msm8996 chipset to enable High speed and Super
speed USB support.

Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>