net: bridge: mcast: account for ipv6 size when dumping querier state

We need to account for the IPv6 attributes when dumping querier state.

Fixes: 5e924fe6ccfd ("net: bridge: mcast: dump ipv6 querier state")
Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>