USB xHCI controllers

Required properties:
  - compatible: should be one or more of

    - "generic-xhci" for generic XHCI device
    - "marvell,armada3700-xhci" for Armada 37xx SoCs
    - "marvell,armada-375-xhci" for Armada 375 SoCs
    - "marvell,armada-380-xhci" for Armada 38x SoCs
    - "brcm,bcm7445-xhci" for Broadcom STB SoCs with XHCI
    - "xhci-platform" (deprecated)

    When compatible with the generic version, nodes must list the
    SoC-specific version corresponding to the platform first
    followed by the generic version.

  - reg: should contain address and length of the standard XHCI
    register set for the device.
  - interrupts: one XHCI interrupt should be described here.

Optional properties:
  - clocks: reference to the clocks
  - clock-names: mandatory if there is a second clock, in this case
    the name must be "core" for the first clock and "reg" for the
    second one
  - usb2-lpm-disable: indicate if we don't want to enable USB2 HW LPM
  - usb3-lpm-capable: determines if platform is USB3 LPM capable
  - quirk-broken-port-ped: set if the controller has broken port disable mechanism
  - imod-interval-ns: default interrupt moderation interval is 5000ns
  - phys : see usb-hcd.yaml in the current directory
  - offload: supporting USB offload feature, 0: disabled, 1: audio

additionally the properties from usb-hcd.yaml (in the current directory) are
supported.


Example:
	usb@f0931000 {
		compatible = "generic-xhci";
		reg = <0xf0931000 0x8c8>;
		interrupts = <0x0 0x4e 0x0>;
	};