tcp/ipv4: remove AF_INET_FAMILY

After commit 079096f1 ("tcp/dccp: install syn_recv requests into ehash table")
the macro isn't used anymore. remove it.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>