usb-linux: Add missing break statement

cppcheck report:
usb-linux.c:661: warning: Redundant assignment of "len" in switch

Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/usb-linux.c b/usb-linux.c
index 36a01ea..0ef1d26 100644
--- a/usb-linux.c
+++ b/usb-linux.c
@@ -659,6 +659,7 @@
                         switch(errno) {
                         case ETIMEDOUT:
                             len = USB_RET_NAK;
+                            break;
                         case EPIPE:
                         default:
                             len = USB_RET_STALL;