usb: pch_udc: Fix the worning log issue at gadget driver remove

When removing a serial gadget driver, the kernel warning message is outputted.
This patch fixed this issue.

The pch_udc driver did not have disconnection processing of gadget.
Signed-off-by: NToshiharu Okada <toshiharu-linux@dsn.okisemi.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/pch_udc.c

@@ -2718,7 +2718,8 @@ int usb_gadget_unregister_driver(struct usb_gadget_driver *driver)
 
 	pch_udc_disable_interrupts(dev, UDC_DEVINT_MSK);
 
-	/* Assues that there are no pending requets with this driver */
+	/* Assures that there are no pending requests with this driver */
+	driver->disconnect(&dev->gadget);
 	driver->unbind(&dev->gadget);
 	dev->gadget.dev.driver = NULL;
 	dev->driver = NULL;