cifs: remove NULL termination from rename target in CIFSSMBRenameOpenFIle

cifs: remove NULL termination from rename target in CIFSSMBRenameOpenFIle

The rename destination isn't supposed to be null terminated. Also,
change the name string arg to be const.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>