staging: nvec: Add myself to MAINTAINERS

I intent to support this code, especially the parts
I wrote; and will thus enter as co-maintainer.

Signed-off-by: Julian Andres Klode <jak@jak-linux.org>
Acked-by: Marc Dietrich <marvin24@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>