[mailmap] Add mailmap entry for myself (#189447)

.mailmap

@@ -33,6 +33,7 @@
 <rnk@llvm.org> <rnk@nvidia.com> <rnk@google.com> <reid@kleckner.net>
 <thakis@chromium.org> <nicolasweber@gmx.de>
 Adarsha Regmi <aregmi@qti.qualcomm.com> <aregmi@quicinc.com>
+Benjamin Maxwell <benjamin.maxwell@arm.com> <macdue@dueutil.tech>
 Brian Cain <brian.cain@oss.qualcomm.com> <bcain@quicinc.com>
 Eli Friedman <efriedma@qti.qualcomm.com> <efriedma@quicinc.com>
 Fateme Hosseini <Fhossein@qti.qualcomm.com> <quic_fhossein@quicinc.com>