MAINTAINERS: add Stefan Mätje as maintainer for the esd electronics GmbH PCIe/402 CAN drivers

Adding myself (Stefan Mätje) as a maintainer for the upcoming driver of
the PCIe/402 interface card family.

Signed-off-by: Stefan Mätje <stefan.maetje@esd.eu>
Link: https://lore.kernel.org/all/20231122160211.2110448-2-stefan.maetje@esd.eu


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>