SMSC USB3503 High-Speed Hub Controller

Required properties:
- compatible: Should be "smsc,usb3503" or "smsc,usb3503a".

Optional properties:
- reg: Specifies the i2c slave address, it is required and should be 0x08
       if I2C is used.
- connect-gpios: Should specify GPIO for connect.
- disabled-ports: Should specify the ports unused.
	'1' or '2' or '3' are available for this property to describe the port
	number. 1~3 property values are possible to be described.
	Do not describe this property if all ports have to be enabled.
- intn-gpios: Should specify GPIO for interrupt.
- reset-gpios: Should specify GPIO for reset.
- initial-mode: Should specify initial mode.
                (1 for HUB mode, 2 for STANDBY mode)
- refclk: Clock used for driving REFCLK signal (optional, if not provided
	the driver assumes that clock signal is always available, its
	rate is specified by REF_SEL pins and a value from the primary
	reference clock frequencies table is used)
- refclk-frequency: Frequency of the REFCLK signal as defined by REF_SEL
	pins (optional, if not provided, driver will not set rate of the
	REFCLK signal and assume that a value from the primary reference
	clock frequencies table is used)

Examples:
	usb3503@08 {
		compatible = "smsc,usb3503";
		reg = <0x08>;
		connect-gpios = <&gpx3 0 1>;
		disabled-ports = <2 3>;
		intn-gpios = <&gpx3 4 1>;
		reset-gpios = <&gpx3 5 1>;
		initial-mode = <1>;
	};
