versatile: remove cannot_destroy_with_object_finalize_yet

cannot_destroy_with_object_finalize_yet was added by 4c315c2
("qdev: Protect device-list-properties against broken devices")
because "realview_pci" and "versatile_pci" were hanging
during "device-list-properties" cleanup (an infinite loop in
bus_unparent()).

We have this problem because the child is not removed from
the list of the PCI bus children because it has no defined parent:
qdev_set_parent_bus() set the device parent_bus pointer to bus, and
adds the device in the bus children list, but doesn't update the
device parent pointer.

To fix the problem, move all the involved parts to the realize function.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20170414083717.13641-4-lvivier@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Peter Maydell <peter.maydell@linaro.org>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
