MAINTAINERS: add German Maglione as virtiofs co-maintainer

MAINTAINERS: add German Maglione as virtiofs co-maintainer

German Maglione is a co-maintainer of the virtiofsd userspace device
implementation (https://gitlab.com/virtio-fs/virtiofsd) and is currently
one of the most active virtiofs developers outside the kernel.

I have not worked on virtiofs except to review kernel patches for a few
years now and would like German to take over from me gradually. It is
healthier to have a kernel maintainer who is actively involved. I expect
to remove myself in a few months.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://patch.msgid.link/20251126211548.598469-1-stefanha@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>