tcp: keepalive cleanups

Introduce keepalive_probes(tp) helper, and use it, like 
keepalive_time_when(tp) and keepalive_intvl_when(tp)

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 88af843..cbb2a48 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1007,6 +1007,11 @@
 	return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
 }
 
+static inline int keepalive_probes(const struct tcp_sock *tp)
+{
+	return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
+}
+
 static inline int tcp_fin_time(const struct sock *sk)
 {
 	int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;