spapr_phb_realize() passes the sPAPR machine state as opaque data
for the I/O callbacks:

memory_region_init_io(&sphb->msiwindow, OBJECT(sphb), &spapr_msi_ops, spapr,
                                                                      ^^^^^
                      "msi", msi_window_size);

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20201209170052.1431440-5-groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>