team: remove synchronize_rcu() called during port disable

Check the unlikely case of team->en_port_count == 0 before modulo
operation.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/team/team_mode_roundrobin.c b/drivers/net/team/team_mode_roundrobin.c
index d268e4d..90311c73 100644
--- a/drivers/net/team/team_mode_roundrobin.c
+++ b/drivers/net/team/team_mode_roundrobin.c
@@ -30,7 +30,8 @@
 	struct team_port *port;
 	int port_index;
 
-	port_index = rr_priv(team)->sent_packets++ % team->en_port_count;
+	port_index = team_num_to_port_index(team,
+					    rr_priv(team)->sent_packets++);
 	port = team_get_port_by_index_rcu(team, port_index);
 	port = team_get_first_port_txable_rcu(team, port);
 	if (unlikely(!port))