mailmap: Update email address

My Netronome address is no longer active. I am no maintainer, but
get_maintainer.pl sometimes returns my name for a small number of
files (BPF-related). Add an entry to .mailmap for good measure.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200226171353.18982-1-quentin@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>