dt: net: enhance DWC EQoS binding to support Tegra186

The Synopsys DWC EQoS is a configurable IP block which supports multiple
options for bus type, clocking and reset structure, and feature list.
Extend the DT binding to define a "compatible value" for the configuration
contained in NVIDIA's Tegra186 SoC, and define some new properties and
list property entries required by that configuration.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Rob Herring <robh@kernel.org>