MAINTAINERS: Remove Olof from SoC maintainers

I haven't been an active participant for a couple of years now, and
after discussions at Linux Plumbers in 2024, Arnd is getting fresh help
from a few more participants.

It's time to remove myself, and spare myself from patches and pull
requests in my inbox.

Signed-off-by: Olof Johansson <olof@lixom.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>