[TCP]: Move __tcp_data_snd_check into tcp_output.c

It reimplements portions of tcp_snd_check(), so it
we move it to tcp_output.c we can consolidate it's
logic much easier in a later change.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 2cbe879..362b811 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -530,6 +530,16 @@
 	tcp_cwnd_validate(sk, tp);
 }
 
+void __tcp_data_snd_check(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (after(TCP_SKB_CB(skb)->end_seq, tp->snd_una + tp->snd_wnd) ||
+	    tcp_packets_in_flight(tp) >= tp->snd_cwnd ||
+	    tcp_write_xmit(sk, tp->nonagle))
+		tcp_check_probe_timer(sk, tp);
+}
+
 int tcp_may_send_now(struct sock *sk, struct tcp_sock *tp)
 {
 	struct sk_buff *skb = sk->sk_send_head;