staging/lustre/libcfs: restore LINVRNT

It was mistakenly removed by coan. Add it back and also with a new
Kconfig option to enable it.

Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>