* Samsung's USB phy built in to some SoCs (like exynos5)

The phy's node in the device tree must be a child of the device tree node for
the USB controller using the phy.

Required properties:
  - compatible: value should be:
      (a) "samsung,exynos-usbphy"

Optional properties:
  - clock-enable-gpio: If present then an external GPIO is used to turn on the
    external clock for the USB phy.  The external clock is needed to get full
    USB 3.0 compliance.  This GPIO is turned off and we move to an internal
    reference clock (which is noisier) when in runtime suspend.
    If this GPIO isn't specified we'll stay with the internal reference clock
    always.

Example (including containing node):
	xhci {
		compatible = "samsung,exynos-xhci";
		reg = <0x12000000 0x10000>;
		interrupts = <0 72 0>;

		samsung,vbus-gpio = <&gpx2 7 1 3 3>;
		phy {
			compatible = "samsung,exynos-usbphy";
			clock-enable-gpio = <&gpy1 1 1 0 3>;
		};
	};
