.mailmap: add an alias for Timo Aaltonen

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/1999>
diff --git a/.mailmap b/.mailmap
index 56764bc..70783fa 100644
--- a/.mailmap
+++ b/.mailmap
@@ -581,6 +581,8 @@
 Timothy Arceri <timothy.arceri@collabora.com> <t_arceri@yahoo.com.au>
 Timothy Arceri <timothy.arceri@collabora.com> Timothy <t_arceri@yahoo.com.au>
 
+Timo Aaltonen <tjaalton@debian.org> <tjaalton@cc.hut.fi>
+
 Tom Fogal <tfogal@alumni.unh.edu> <tfogal@sci.utah.edu>
 
 Tom Stellard <thomas.stellard@amd.com> <tstellar@gmail.com>