bridge: fix br_multicast_query_expired() bug

bridge: fix br_multicast_query_expired() bug

br_multicast_query_expired() querier argument is a pointer to
a struct bridge_mcast_querier :

struct bridge_mcast_querier {
        struct br_ip addr;
        struct net_bridge_port __rcu    *port;
};

Intent of the code was to clear port field, not the pointer to querier.

Fixes: 2cd4143192e8 ("bridge: memorize and export selected IGMP/MLD querier port")
Signed-off-by: Eric Dumazet <[email protected]>
Acked-by: Thadeu Lima de Souza Cascardo <[email protected]>
Acked-by: Linus Lüssing <[email protected]>
Cc: Linus Lüssing <[email protected]>
Cc: Steinar H. Gunderson <[email protected]>
Signed-off-by: David S. Miller <[email protected]>