usb: gadget: composite: add reset API at usb_gadget_driver

Add reset API at usb_gadget_driver, it calls disconnect handler currently,
but may do different things in future.
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/composite.c

@@ -2073,6 +2073,7 @@ static const struct usb_gadget_driver composite_driver_template = {
 	.unbind		= composite_unbind,
 
 	.setup		= composite_setup,
+	.reset		= composite_disconnect,
 	.disconnect	= composite_disconnect,
 
 	.suspend	= composite_suspend,