MAINTAINERS: remove myself as ppc maintainer/reviewer

MAINTAINERS: remove myself as ppc maintainer/reviewer

It has been awhile since I actively did anything for qemu-ppc aside from
reading the qemu-ppc inbox a couple of times each month. It's not enough
to justify a reviewer role, let alone being a maintainer.

Given that we're doing qemu-ppc maintainership changes across the board
I'll take the opportunity and remove myself from the premises too. Feel
free to reach out with questions about code I did in the past, but at
this moment I'm no longer able to keep up with qemu-ppc activities.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250724123416.3115941-1-danielhb413@gmail.com
[ clg: Adjusted context ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>