MAINTAINERS: step down as vfio reviewer

MAINTAINERS: step down as vfio reviewer

As my focus has shifted in recent months, my involvement with vfio has
decreased to occasionally reviewing some simpler patches, which is
probably less than you'd expect when you cc: someone for review.

Given that I currently don't have spare time to invest in looking at
vfio things, let's adjust the entry to match reality.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/20230112145707.27941-1-cohuck@redhat.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>