usb: udc-core: set gadget state as not attached after unloading module

Set gadget state as "not attached" after unloading gadget module, or
its state will be unchanged after we unload gadget module.

Signed-off-by: Peter Chen <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/gadget/udc-core.c

···
 	list_for_each_entry(udc, &udc_list, list)
 		if (udc->driver == driver) {
 			usb_gadget_remove_driver(udc);
+			usb_gadget_set_state(udc->gadget,
+					USB_STATE_NOTATTACHED);
 			ret = 0;
 			break;
 		}