net: stmmac: dwc-qos: Add Tegra186 support

The NVIDIA Tegra186 SoC contains an instance of the Synopsys DWC
ethernet QOS IP core. The binding that it uses is slightly different
from existing ones because of the integration (clocks, resets, ...).

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>