usb: gadget: pxa25x: fix disconnect reporting

when commit 6166c24 (usb: gadget: pxa25x_udc:
convert to udc_start/udc_stop) converted
this driver to udc_start/udc_stop, it failed
to consider the fact that stop_activity()
is called from disconnect interrupt.

Fix the problem so that gadget drivers know
about proper disconnect sequences.

Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/pxa25x_udc.c b/drivers/usb/gadget/pxa25x_udc.c
index 9aa9dd5..d0f3748 100644
--- a/drivers/usb/gadget/pxa25x_udc.c
+++ b/drivers/usb/gadget/pxa25x_udc.c
@@ -1303,6 +1303,10 @@
 	}
 	del_timer_sync(&dev->timer);
 
+	/* report disconnect; the driver is already quiesced */
+	if (driver)
+		driver->disconnect(&dev->gadget);
+
 	/* re-init driver-visible data structures */
 	udc_reinit(dev);
 }