phy: omap-usb2: Add clock names to Documentation binding

 - reg : Address and length of the register set for the device.

 - #phy-cells: determine the number of cells that should be given in the

   phandle while referencing this phy.

 - clocks: a list of phandles and clock-specifier pairs, one for each entry in

   clock-names.

 - clock-names: should include:

   * "wkupclk" - wakeup clock.

   * "refclk" - reference clock (optional).

Optional properties:

 - ctrl-module : phandle of the control module used by PHY driver to power on

	reg = <0x4a0ad080 0x58>;

	ctrl-module = <&omap_control_usb>;

	#phy-cells = <0>;

	clocks = <&usb_phy_cm_clk32k>, <&usb_otg_ss_refclk960m>;

	clock-names = "wkupclk", "refclk";

};

TI PIPE3 PHY