Xilinx USB EHCI controller

Required properties:
- compatible: must be "xlnx,xps-usb-host-1.00.a"
- reg: physical base address of the controller and length of memory mapped
  region.
- interrupts: The EHCI interrupt

Optional properties:
- xlnx,ext-vbus-valid: Use external VBUS
- xlnx,support-usb-fs: Support for Full Speed USB
- xlnx,use-phy-bus-pwr: Use phy bus power in USB

Example:

	xps_usb_host_0: usb@82400000 {
		compatible = "xlnx,xps-usb-host-1.00.a";
		interrupt-parent = <&xps_intc_0>;
		interrupts = < 0 2 >;
		reg = < 0x82400000 0x200 >;
	} ;
