.mailmap: add an alias for Boris Brezillon

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/1999>
diff --git a/.mailmap b/.mailmap
index 3b094ca..aa67d3b 100644
--- a/.mailmap
+++ b/.mailmap
@@ -78,6 +78,8 @@
 
 Blair Sadewitz <blair.sadewitz@gmail.com> Blair Sadewitz <blair.sadewitz.gmail.com>
 
+Boris Brezillon <boris.brezillon@collabora.com> <boris.brezillon@free-electrons.com>
+
 Boris Peterbarg <reist@users.sourceforge.net> reist <reist>
 
 Brian Paul <brianp@vmware.com> Brian <brian.paul@tungstengraphics.com>