MAINTAINERS: Assume maintainership of PL111

Emma Anholt dropped maintainership for PL111 and I
didn't notice it at the time. I've written part of it
and I'm happy to maintain it, list myself as maintainer
and assume active maintainership.

Acked-by: Simona Vetter <simona.vetter@ffwll.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241219-pl111-maintain-v1-1-c60f57c523cd@linaro.org