MAINTAINERS: Add entries for Siemens IPC modules

There are different IPC driver modules in the kernel that are actively
maintained by Siemens but not yet listed in the MAINTAINERS file.
Add the missing entries.

Signed-off-by: Gerd Haeussler <gerd.haeussler.ext@siemens.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230814073114.2885-1-haeussler.gerd@gmail.com


Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>