tcp: remove conditional branches from tcp_mstamp_refresh()

tcp_clock_ns() (aka ktime_get_ns()) is using monotonic clock,
so the checks we had in tcp_mstamp_refresh() are no longer
relevant.

This patch removes cpu stall (when the cache line is not hot)
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_output.c

@@ -52,12 +52,8 @@ void tcp_mstamp_refresh(struct tcp_sock *tp)
 {
 	u64 val = tcp_clock_ns();
 
-	if (val > tp->tcp_clock_cache)
-		tp->tcp_clock_cache = val;
-
-	val = div_u64(val, NSEC_PER_USEC);
-	if (val > tp->tcp_mstamp)
-		tp->tcp_mstamp = val;
+	tp->tcp_clock_cache = val;
+	tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
 }
 
 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,