This patch converts the OpenPIC device to qdev. Along the way it
renames the "openpic" target to "raven" and the "mpic" target to
"fsl_mpic_20", to better reflect the actual models they implement.

This way we have a generic OpenPIC device now that can handle
different flavors of the OpenPIC specification.
Signed-off-by: NAlexander Graf <agraf@suse.de>