mailmap: add entries for Mat Martineau

Map Mat's old corporate addresses to his kernel.org one.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Link: https://lore.kernel.org/r/20230418-upstream-net-20230418-mailmap-mat-v1-1-13ca5dc83037@tessares.net


Signed-off-by: Jakub Kicinski <kuba@kernel.org>