mailmap: Add entry for Greg Kurz

I had stopped using gkurz@linux.vnet.ibm.com a while back already but
this email address was shutdown last June when I quit IBM. It's about
time to map it to groug@kaod.org.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <159724665142.75339.817685642171828648.stgit@bahia.lan>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

.mailmap

@@ -48,6 +48,7 @@ Alexander Graf <agraf@csgraf.de> <agraf@suse.de>
 Anthony Liguori <anthony@codemonkey.ws> Anthony Liguori <aliguori@us.ibm.com>
 Filip Bozuta <filip.bozuta@syrmia.com> <filip.bozuta@rt-rk.com.com>
 Frederic Konrad <konrad@adacore.com> <fred.konrad@greensocs.com>
+Greg Kurz <groug@kaod.org> <gkurz@linux.vnet.ibm.com>
 James Hogan <jhogan@kernel.org> <james.hogan@imgtec.com>
 Leif Lindholm <leif@nuviainc.com> <leif.lindholm@linaro.org>
 Radoslaw Biernacki <rad@semihalf.com> <radoslaw.biernacki@linaro.org>