arm64: tegra: Add ethernet support for Tegra186

The NVIDIA Tegra186 SoC contains an instance of the Synopsys DWC
ethernet QOS IP block, which supports 10, 100 and 1000 Mbps data
transfer rates.

Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>