7360: add&fix downgrade image names, thx [http://www.da-cube.net/showthread.php/6950-ruKernelTool-quot-das-quot-Universal-Flash-Upload-und-Recovery-Tool-für-AVM-Fritzboxen/ Andi_84 @DaCube]

git-svn-id: file:///var/svn/freetz/trunk@10276 149334a1-2f27-0410-a3b9-fc62619ac1e6