dt-bindings: phy: tegra: Add Tegra186 support

Extend the bindings to cover the set of features found in Tegra186. Note
that, technically, there are four more supplies connected to the XUSB
pad controller (DVDD_PEX, DVDD_PEX_PLL, HVDD_PEX and HVDD_PEX_PLL), but
the power sequencing requirements of Tegra186 require these to be under
the control of the PMIC.

Reviewed-by: JC Kuo <jckuo@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>