spapr_drc: Change value of property "fdt" from null back to {}
prop_get_fdt() misuses the visitor API: when fdt is null, it doesn't
visit anything. object_property_get_qobject() happily
object_property_get_qobject(). Amazingly, the latter survives the
misuse. Turns out we've papered over it long before prop_get_fdt()
existed, in commit
1d10b44.
However, commit
6c2f9a1 changed how we paper over it, and as a side
effect changed qom-get's value from {} to null. Change it right back
by fixing the visitor misuse.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>