scsi: Pass size to scsi_bus_new()

To be passed to qbus_create_inplace().

Use DEVICE() casts instead of direct parent field access.

Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
diff --git a/hw/scsi/spapr_vscsi.c b/hw/scsi/spapr_vscsi.c
index e9090e5..b2fcd4b 100644
--- a/hw/scsi/spapr_vscsi.c
+++ b/hw/scsi/spapr_vscsi.c
@@ -1020,7 +1020,8 @@
 
     dev->crq.SendFunc = vscsi_do_crq;
 
-    scsi_bus_new(&s->bus, &dev->qdev, &vscsi_scsi_info, NULL);
+    scsi_bus_new(&s->bus, sizeof(s->bus), DEVICE(dev),
+                 &vscsi_scsi_info, NULL);
     if (!dev->qdev.hotplugged) {
         scsi_bus_legacy_handle_cmdline(&s->bus, &err);
         if (err != NULL) {