tcp: add init_req method to tcp_request_sock_ops

Move the specific IPv4/IPv6 intializations to a new method in
tcp_request_sock_ops in preparation for unifying tcp_v4_conn_request
and tcp_v6_conn_request.

Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -1613,6 +1613,8 @@ struct tcp_request_sock_ops {
 						  const struct request_sock *req,
 						  const struct sk_buff *skb);
 #endif
+	void (*init_req)(struct request_sock *req, struct sock *sk,
+			 struct sk_buff *skb);
 };
 
 int tcpv4_offload_init(void);