Samsung Exynos SoC USB controller

The USB devices interface with USB controllers on Exynos SOCs.
The device node has following properties.

EHCI
Required properties:
 - compatible: should be "samsung,exynos4210-ehci" for USB 2.0
   EHCI controller in host mode.
 - reg: physical base address of the controller and length of memory mapped
   region.
 - interrupts: interrupt number to the cpu.
 - clocks: from common clock binding: handle to usb clock.
 - clock-names: from common clock binding: Shall be "usbhost".

Optional properties:
 - samsung,vbus-gpio:  if present, specifies the GPIO that
   needs to be pulled up for the bus to be powered.

Example:

	usb@12110000 {
		compatible = "samsung,exynos4210-ehci";
		reg = <0x12110000 0x100>;
		interrupts = <0 71 0>;
		samsung,vbus-gpio = <&gpx2 6 1 3 3>;

		clocks = <&clock 285>;
		clock-names = "usbhost";
	};

OHCI
Required properties:
 - compatible: should be "samsung,exynos4210-ohci" for USB 2.0
   OHCI companion controller in host mode.
 - reg: physical base address of the controller and length of memory mapped
   region.
 - interrupts: interrupt number to the cpu.
 - clocks: from common clock binding: handle to usb clock.
 - clock-names: from common clock binding: Shall be "usbhost".

Example:
	usb@12120000 {
		compatible = "samsung,exynos4210-ohci";
		reg = <0x12120000 0x100>;
		interrupts = <0 71 0>;

		clocks = <&clock 285>;
		clock-names = "usbhost";
	};
