Renesas Electronics USBHS driver

Required properties:
  - compatible: Must contain one of the following:
	- "renesas,usbhs-r8a7790"
	- "renesas,usbhs-r8a7791"
	- "renesas,usbhs-r8a7794"
  - reg: Base address and length of the register for the USBHS
  - interrupts: Interrupt specifier for the USBHS
  - clocks: A list of phandle + clock specifier pairs

Optional properties:
  - renesas,buswait: Integer to use BUSWAIT register
  - renesas,enable-gpio: A gpio specifier to check GPIO determining if USB
			 function should be enabled
  - phys: phandle + phy specifier pair
  - phy-names: must be "usb"
  - dmas: Must contain a list of references to DMA specifiers.
  - dma-names : named "ch%d", where %d is the channel number ranging from zero
                to the number of channels (DnFIFOs) minus one.

Example:
	usbhs: usb@e6590000 {
		compatible = "renesas,usbhs-r8a7790";
		reg = <0 0xe6590000 0 0x100>;
		interrupts = <0 107 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&mstp7_clks R8A7790_CLK_HSUSB>;
	};