mailmap: Add Simon Arlott (replacement for expired email address)

Add replacement email address for the one on my expired domain.
Signed-off-by: Simon Arlott <simon@octiron.net>
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>

.mailmap

@@ -229,6 +229,7 @@ Shuah Khan <shuah@kernel.org> <shuahkhan@gmail.com>
 Shuah Khan <shuah@kernel.org> <shuah.khan@hp.com>
 Shuah Khan <shuah@kernel.org> <shuahkh@osg.samsung.com>
 Shuah Khan <shuah@kernel.org> <shuah.kh@samsung.com>
+Simon Arlott <simon@octiron.net> <simon@fire.lp0.eu>
 Simon Kelley <simon@thekelleys.org.uk>
 Stéphane Witzmann <stephane.witzmann@ubpmes.univ-bpclermont.fr>
 Stephen Hemminger <shemminger@osdl.org>