Broadcom STB USB PHY

Required properties:
- compatible: "brcm,brcmstb-usb-phy" - Standard STB SoC's
  	      "brcm,bcm7216-usb-phy" - SoC's with the new Synopsis controller
  	      "brcm,bcm7211-usb-phy" - 7211 SoC with Synopsis controller
- reg: a list of offset and length pairs.
- reg-names: "ctrl" - Required for all systems
  	     "xhci_ec" - Required for systems with an XHCI controller
	     "xhci_gbl - Required for systems with the new Synopsis controller
  
- #phy-cells: Shall be 1 as it expects one argument for setting
	      the type of the PHY. Possible values are:
	      - 0 for USB1.1/2.0 PHY
	      - 1 for USB3.x PHY

Optional Properties:
- clocks : clock phandles.
- clock-names: String, clock name.
- ipp: Boolean, Invert Port Power.
  Possible values are: 0 (Don't invert), 1 (Invert)
- ioc: Boolean, Invert Over Current detection.
  Possible values are: 0 (Don't invert), 1 (Invert)
- has-xhci: Boolean indicating the phy has an XHCI phy.
- has-xhci-only: Boolean indicating the phy has an XHCI phy and no
  EHCI/OHCI phy.
- device: String, PHY Device mode.
  Possible values are: "off", "on ", "dual" or "typec-pd"
  If this property is not defined, the phy will default to "off" mode.

Example:

usbphy_0: usb-phy@f0470200 {
	reg = <0xf0470200 0xb8>,
		<0xf0471940 0x6c0>;
	reg-names "ctrl", "xhci_ec"
	compatible = "brcm,brcmstb-usb-phy";
	#phy-cells = <1>;
	device = "off"
	ioc = <1>;
	ipp = <1>;
	has-xhci;
	clocks = <&usb20>, <&usb30>;
	clock-names = "sw_usb", "sw_usb3";
};
