dt-bindings: usb: Restart host mode in high speed

It is required to restart usb host mode in high speed on platforms not
supporting usb3 ss and DP concurrency. Hence add pd20only as source
to restart host mode in high speed for those platforms, when dp is
detected through discovery of svids.

Change-Id: I563b2213fa2739909f29d0f61e7424297e495f6c