audit: add Paul Moore to the MAINTAINERS entry

After a long stint maintaining the audit tree, Eric asked me to step
in and handle the day-to-day management of the audit tree.  We should
also update the linux-audit mailing list entry to better reflect
current usage.

Signed-off-by: Paul Moore <pmoore@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>