Maxim Integrated SPI-based USB 2.0 host controller MAX3421E

Required properties:
 - compatible: Should be "maxim,max3421"
 - spi-max-frequency: maximum frequency for this device must not exceed 26 MHz.
 - reg: chip select number to which this device is connected.
 - maxim,vbus-en-pin: <GPOUTx ACTIVE_LEVEL>
   GPOUTx is the number (1-8) of the GPOUT pin of MAX3421E to drive Vbus.
   ACTIVE_LEVEL is 0 or 1.
 - interrupts: the interrupt line description for the interrupt controller.
   The driver configures MAX3421E for active low level triggered interrupts,
   configure your interrupt line accordingly.

Example:

	usb@0 {
		compatible = "maxim,max3421";
		reg = <0>;
		maxim,vbus-en-pin = <3 1>;
		spi-max-frequency = <26000000>;
		interrupt-parent = <&PIC>;
		interrupts = <42>;
	};
