usb: dwc3: Add USB host OTG capability

On some targets like 9x35, the ID notification is wired via
SMB. Add here the support of getting external ID
notification and by this allowing the capability of
switching host-device and vice versa on the go.

Change-Id: I37c2a68b9b355ee8c0e39627aeff82c14566f636
Signed-off-by: Lena Salman <esalman@codeaurora.org>