USB: core: Add support for OTG automated compliance tests

1. Add OTG PET device to TPL. OTG device shall support this
device for allowing compliance automated testing.

2. Add otg_srp_reqd filed to gadget. OTG B-device shall enable
this flag when OTG PET (Protocol and Electrical Tester) that
acts as A-device sends Set Feature TEST_MODE with wIndex high
byte value = 0x06.  OTG PET expects B-device to initiate SRP
after the end of current session.

3. Add otg_vbus_off to usb_bus.  USB core enables this flag
when OTG PET enumerates with bcdDevice[0] field in its Device
Descriptor is equal to 1.  OTG PET expects A-device to turn off
the VBUS with in 5 sec of its disconnection which allows it to
initiate SRP.

3. Add support to identify OTG PET and start HNP quickly.

Change-Id: Ib1f4d835d00ca29ff8f980c94d75a3890507dedc
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>