.mailmap: Update Alexander Graf email address

Update Alexander Graf email address to avoid emails bouncing.

Suggested-by: Alexander Graf <agraf@csgraf.de>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alexander Graf <agraf@csgraf.de>
Message-Id: <20200702173818.14651-2-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

.mailmap

@@ -44,6 +44,7 @@ Aleksandar Markovic <aleksandar.qemu.devel@gmail.com> <aleksandar.markovic@imgte
 Aleksandar Markovic <aleksandar.qemu.devel@gmail.com> <amarkovic@wavecomp.com>
 Aleksandar Rikalo <aleksandar.rikalo@syrmia.com> <arikalo@wavecomp.com>
 Aleksandar Rikalo <aleksandar.rikalo@syrmia.com> <aleksandar.rikalo@rt-rk.com>
+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>