Do not bother with bogonsv6 when interface does not have any ipaddrv6 type

We can further reduce the use cases when the bogonsv6 table needs to be used in pf.
If an interface has no IPv6 address type specified, then it simply cannot have an IPv6 packet received and passed to pf for processing, so there is no way that the bogonsv6 table would ever be matched. Therefore do not bother loading bogonsv6 in this case. I think this reasoning is correct?
This is the change for 2.1 branch.