tcp: fix tcp_release_cb() to dispatch via address family for mtu_reduced()

tcp: fix tcp_release_cb() to dispatch via address family for mtu_reduced()

Make sure we use the correct address-family-specific function for
handling MTU reductions from within tcp_release_cb().

Previously AF_INET6 sockets were incorrectly always using the IPv6
code path when sometimes they were handling IPv4 traffic and thus had
an IPv4 dst.

Signed-off-by: Neal Cardwell <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Diagnosed-by: Willem de Bruijn <[email protected]>
Fixes: 563d34d057862 ("tcp: dont drop MTU reduction indications")
Reviewed-by: Hannes Frederic Sowa <[email protected]>
Signed-off-by: David S. Miller <[email protected]>