ARM: s32c: update MAINTAINERS entry

As discussed on the mailing list, Chester is stepping down from being
the primary maintainer for the s32c platform, and Ghennadi becomes an
additional reviewer.

For the moment, there is no full maintainer for s32c, but Shawn is already
listed as the overall maintainer for 32-bit freescale/nxp platforms
(except layerscape and qoriq) and agreed to merge s32c patches as they
come in and are reviewed by the remaining reviewers.

Adapt the entries in the maintainers file based on the discussion.

Reviewed-by: Matthias Brugger <mbrugger@suse.com>
Reviewed-by: Ghennadi Procopciuc <ghennadi.procopciuc@oss.nxp.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Chester Lin <chester62515@gmail.com>
Cc: Matthias Brugger <mbrugger@suse.com>
Cc: Ghennadi Procopciuc <ghennadi.procopciuc@oss.nxp.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: NXP S32 Linux Team <s32@nxp.com>
Link: https://lore.kernel.org/all/20240221120123.1118552-1-ghennadi.procopciuc@oss.nxp.com/
Link: https://lore.kernel.org/r/20240304204249.936140-1-arnd@kernel.org


Signed-off-by: Arnd Bergmann <arnd@arndb.de>