doc: usb: ci-hdrc-usb2: Add pinctrl properties for HSIC pin groups

  controller. It's expected that a mux state of 0 indicates device mode and a

  mux state of 1 indicates host mode.

- mux-control-names: Shall be "usb_switch" if mux-controls is specified.

- pinctrl-names: Names for optional pin modes in "default", "host", "device"

- pinctrl-names: Names for optional pin modes in "default", "host", "device".

  In case of HSIC-mode, "idle" and "active" pin modes are mandatory. In this

  case, the "idle" state needs to pull down the data and strobe pin

  and the "active" state needs to pull up the strobe pin.

- pinctrl-n: alternate pin modes

i.mx specific properties

		mux-controls = <&usb_switch>;

		mux-control-names = "usb_switch";

	};

Example for HSIC:

	usb@2184400 {

		compatible = "fsl,imx6q-usb", "fsl,imx27-usb";

		reg = <0x02184400 0x200>;

		interrupts = <0 41 IRQ_TYPE_LEVEL_HIGH>;

		clocks = <&clks IMX6QDL_CLK_USBOH3>;

		fsl,usbphy = <&usbphynop1>;

		fsl,usbmisc = <&usbmisc 2>;

		phy_type = "hsic";

		dr_mode = "host";

		ahb-burst-config = <0x0>;

		tx-burst-size-dword = <0x10>;

		rx-burst-size-dword = <0x10>;

		pinctrl-names = "idle", "active";

		pinctrl-0 = <&pinctrl_usbh2_idle>;

		pinctrl-1 = <&pinctrl_usbh2_active>;

		#address-cells = <1>;

		#size-cells = <0>;

		usbnet: smsc@1 {

			compatible = "usb424,9730";

			reg = <1>;

		};

	};