What:		/sys/bus/platform/devices/5b110000.usb3/role
Date:		Jan 2019
Contact:	Peter Chen <peter.chen@nxp.com>
Description:
		It returns string "gadget", "host" and "none" when read it,
		it indicates current controller role.

		It will do role switch when write "gadget" or "host" to it.
		Only controller at dual-role configuration supports writing.