greybus: es1-ap-usb: handle -EPROTO in check_urb_status()

On a disconnect we can also have a status of -EPROTO. This results in
a flood of error messages due to the -EAGAIN handling of unsupported
status results. Fix this by also returning status when we have -EPROTO.
Signed-off-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/es1-ap-usb.c

@@ -257,6 +257,7 @@ static int check_urb_status(struct urb *urb)
 	case -ENOENT:
 	case -ESHUTDOWN:
 	case -EILSEQ:
+	case -EPROTO:
 		/* device is gone, stop sending */
 		return status;
 	}