spapr: Don't use qdev_get_machine() in spapr_msi_write()

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>

hw/ppc/spapr_pci.c

@@ -747,7 +747,7 @@ static PCIINTxRoute spapr_route_intx_pin_to_irq(void *opaque, int pin)
 static void spapr_msi_write(void *opaque, hwaddr addr,
                             uint64_t data, unsigned size)
 {
-    SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
+    SpaprMachineState *spapr = opaque;
     uint32_t irq = data;
 
     trace_spapr_pci_msi_write(addr, data, irq);