Specifically add listing, injection of event channels.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>