libmodmount / do_umount_locked:
 * eliminate 2nd parameter (derive it from the 1st one) - since 5.2x AVM passes just one parameter to it
 * refs #2572


git-svn-id: file:///var/svn/freetz/trunk@12551 149334a1-2f27-0410-a3b9-fc62619ac1e6