AUTHORS: Add Martin Varghese.

Signed-off-by: Ben Pfaff <blp@ovn.org>

AUTHORS.rst

@@ -259,6 +259,7 @@ Markos Chandras                    mchandras@suse.de
 Martin Casado                      casado@cs.stanford.edu
 Martin Fong                        mwfong@csl.sri.com
 Martino Fornasa                    mf@fornasa.it
+Martin Varghese                    martin.varghese@nokia.com
 Martin Xu                          martinxu9.ovs@gmail.com
 Martin Zhang                       martinbj2008@gmail.com
 Maryam Tahhan                      maryam.tahhan@intel.com