.mailmap: add an alias for Alan Swanson

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/1999>
diff --git a/.mailmap b/.mailmap
index 7f0a3fb..ffd5e8c 100644
--- a/.mailmap
+++ b/.mailmap
@@ -6,6 +6,8 @@
 Adrian Marius Negreanu <adrian.m.negreanu@intel.com> Adrian Negreanu <adrian.m.negreanu@intel.com>
 Adrian Marius Negreanu <adrian.m.negreanu@intel.com> Negreanu Marius Adrian <adrian.m.negreanu@intel.com>
 
+Alan Swanson <reiver@improbability.net> <swanson@ukfsn.org>
+
 Dave Airlie <airlied@redhat.com> <airliedfreedesktop.org>
 Dave Airlie <airlied@redhat.com> airlied <airlied@unused-12-215.bne.redhat.com>
 Dave Airlie <airlied@redhat.com> <airlied@dhcp-1-203.bne.redhat.com>