@pako69: I just ran into the same issue, turns out you only need to include “patch” once in the command:
patch -b -i simple-ldap-login.multisite.patch
Make sure it’s in the directory created under plugins/ when you installed simple-ldap-login (should just be called simple-ldap-login/). Running this I get:
patch -b -i simple-ldap-login.multisite.patch
patching file Simple-LDAP-Login-Admin.php
patching file Simple-LDAP-Login.php
