savevm: Add DeviceState param

When available, we'd like to be able to access the DeviceState
when registering a savevm.  For buses with a get_dev_path()
function, this will allow us to create more unique savevm
id strings.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/vmware_vga.c b/hw/vmware_vga.c
index bf2a699..359e5d8 100644
--- a/hw/vmware_vga.c
+++ b/hw/vmware_vga.c
@@ -1169,7 +1169,7 @@
 
     vga_common_init(&s->vga, vga_ram_size);
     vga_init(&s->vga);
-    vmstate_register(0, &vmstate_vga_common, &s->vga);
+    vmstate_register(NULL, 0, &vmstate_vga_common, &s->vga);
 
     vga_init_vbe(&s->vga);