net: use ktime_get_ns() and ktime_get_real_ns() helpers

ktime_get_ns() replaces ktime_to_ns(ktime_get())

ktime_get_real_ns() replaces ktime_to_ns(ktime_get_real())

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index de88c4a..0b634e7 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -358,7 +358,7 @@
 
 	tstamp = nf_conn_tstamp_find(ct);
 	if (tstamp && tstamp->stop == 0)
-		tstamp->stop = ktime_to_ns(ktime_get_real());
+		tstamp->stop = ktime_get_real_ns();
 
 	if (nf_ct_is_dying(ct))
 		goto delete;