USB: at91_udc: Cleanup variables after failure in usb_gadget_register_driver()

This patch zeroes some variables when usb_gadget_register_driver()
fails. gadgetfs does a dummy registration to get the name of the USB
driver and then waits for user-land driver. If someone plugs the cable
in the meantime, bad things happen, because at91_udc has been left in
inconsistent state.
Signed-off-by: NWojtek Kaniewski <wojtekka@toxygen.net>
Acked-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Cc: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/at91_udc.c

@@ -1601,6 +1601,10 @@ int usb_gadget_register_driver (struct usb_gadget_driver *driver)
 	if (retval) {
 		DBG("driver->bind() returned %d\n", retval);
 		udc->driver = NULL;
+		udc->gadget.dev.driver = NULL;
+		udc->gadget.dev.driver_data = NULL;
+		udc->enabled = 0;
+		udc->selfpowered = 0;
 		return retval;
 	}