batman-adv: use seq_puts instead of seq_printf when the format is constant

As reported by checkpatch, seq_puts has to be preferred with
respect to seq_printf when the format is a constant string
(no va_args)

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 34f99a4..f105219 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -500,7 +500,7 @@
 	rcu_read_unlock();
 
 	if (gw_count == 0)
-		seq_printf(seq, "No gateways in range ...\n");
+		seq_puts(seq, "No gateways in range ...\n");
 
 out:
 	if (primary_if)