MAINTAINERS: vfio-ccw: Remove myself as the maintainer

I will not be able to continue with my maintainership responsibilities
going forward, so remove myself as the maintainer.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Message-Id: <355a4ac2923ff3dcf2171cb23d477440bd010b34.1564003698.git.alifm@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>