pc-dimm: pass PCDIMMDevice to pc_dimm_.*plug

We're plugging/unplugging a PCDIMMDevice, so directly pass this type
instead of a more generic DeviceState.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20181005092024.14344-5-david@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
4 files changed