media: hantro: Replace maintainers

As per a long time request from Ezequiel, who left the project around
2020, replace the top maintainers with Benjamin and myself, and also
keeping Philipp, who is still active in the subsystem.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>