MAINTAINERS: Add Andrea Mayer as a maintainer of SRv6

Andrea has made significant contributions to SRv6 support in Linux.
Acknowledge the work and on-going interest in Srv6 support with a
maintainers entry for these files so hopefully he is included
on patches going forward.

Signed-off-by: David Ahern <dsahern@kernel.org>
Acked-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Link: https://patch.msgid.link/20250312092212.46299-1-dsahern@kernel.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>