[3.13-stable only] ipv6: fix swapped ipv4/ipv6 mtu_reduced callbacks

Fixes up 4fab9071 ("tcp: fix tcp_release_cb() to dispatch via address
family for mtu_reduced()") backport which has swapped ipv4/ipv6 callbacks
for native IPv6 and mapped IPv4 sockets.

BugLink: http://bugs.launchpad.net/bugs/1404558Signed-off-by: Andy Whitcroft <apw@canonical.com>
Fixes: e86507f2Signed-off-by: Kamal Mostafa <kamal@canonical.com>

net/ipv6/tcp_ipv6.c

@@ -1640,7 +1640,7 @@ static const struct inet_connection_sock_af_ops ipv6_specific = {
 	.compat_setsockopt = compat_ipv6_setsockopt,
 	.compat_getsockopt = compat_ipv6_getsockopt,
 #endif
-	.mtu_reduced	   = tcp_v4_mtu_reduced,
+	.mtu_reduced	   = tcp_v6_mtu_reduced,
 };
 
 #ifdef CONFIG_TCP_MD5SIG
@@ -1672,7 +1672,7 @@ static const struct inet_connection_sock_af_ops ipv6_mapped = {
 	.compat_setsockopt = compat_ipv6_setsockopt,
 	.compat_getsockopt = compat_ipv6_getsockopt,
 #endif
-	.mtu_reduced	   = tcp_v6_mtu_reduced,
+	.mtu_reduced	   = tcp_v4_mtu_reduced,
 };
 
 #ifdef CONFIG_TCP_MD5SIG