virtio-pmem: add myself as virtio-pmem maintainer

Adding myself as virtio-pmem maintainer and also adding virtualization
mailing list entry for virtio specific bits. Helps to get notified for
appropriate bug fixes & enhancements.

Signed-off-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Link: https://lore.kernel.org/r/20211016090646.371145-1-pankaj.gupta.linux@gmail.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>