usb: tegra: Add vbus-supply property for host mode PHYs

Document vbus-supply as an optional property for host mode phy-tegra-usb PHYs.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

diff --cc Documentation/devicetree/bindings/usb/nvidia,tegra20-usb-phy.txt
Simple merge