dt-bindings: phy: tegra-xusb: Add nvidia,pmc prop

This commit describes the "nvidia,pmc" property for Tegra210 tegra-xusb
PHY driver. It is a phandle and specifier referring to the Tegra210
pmc@7000e400 node.
Signed-off-by: JC Kuo <jckuo@nvidia.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt

@@ -54,6 +54,7 @@ For Tegra210:
 - avdd-pll-uerefe-supply: PLLE reference PLL power supply. Must supply 1.05 V.
 - dvdd-pex-pll-supply: PCIe/USB3 PLL power supply. Must supply 1.05 V.
 - hvdd-pex-pll-e-supply: High-voltage PLLE power supply. Must supply 1.8 V.
+- nvidia,pmc: phandle and specifier referring to the Tegra210 PMC node.
 
 For Tegra186:
 - avdd-pll-erefeut-supply: UPHY brick and reference clock as well as UTMI PHY