MAINTAINERS: Update KCONFIG entry

Roman Zippel hasn't been active for several years. Add myself as kconfig
maintainer, but change the mode to "Odd Fixes" to not set expectations
too high. Also, remove the patchwork link, since it is not used for
kbuild/kconfig.

Signed-off-by: Michal Marek <mmarek@suse.cz>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>