doc: dt-binding: usb: add otg related properties

			"peripheral" and "otg". In case this attribute isn't

			passed via DT, USB DRD controllers should default to

			OTG.

 - otg-rev: tells usb driver the release number of the OTG and EH supplement

			with which the device and its descriptors are compliant,

			in binary-coded decimal (i.e. 2.0 is 0200H). This

			property is used if any real OTG features(HNP/SRP/ADP)

			is enabled, if ADP is required, otg-rev should be

			0x0200 or above.

 - hnp-disable: tells OTG controllers we want to disable OTG HNP, normally HNP

			is the basic function of real OTG except you want it

			to be a srp-capable only B device.

 - srp-disable: tells OTG controllers we want to disable OTG SRP, SRP is

			optional for OTG device.

 - adp-disable: tells OTG controllers we want to disable OTG ADP, ADP is

			optional for OTG device.

This is an attribute to a USB controller such as:

	usb-phy = <&usb2_phy>, <&usb3,phy>;

	maximum-speed = "super-speed";

	dr_mode = "otg";

	otg-rev = <0x0200>;

	adp-disable;

};