pci_bridge: manually destroy memory regions within PCIBridgeWindows
The regions are destroyed and recreated on configuration space accesses.
We need to destroy them before the containing PCIBridgeWindows object
is freed.
Reported-by: Gonglei <arei.gonglei@huawei.com> Reported-by: Knut Omang <knut.omang@oracle.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>