net/mlx4_en: Fix off-by-one in counters manipulation

This caused the en_stats_adder helper to accumulate a field which is
not related to the counter, fix that.

Fixes: a3333b35da16 ('net/mlx4_en: Moderate ethtool callback to show [..]')
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_port.c b/drivers/net/ethernet/mellanox/mlx4/en_port.c
index 54f0e5a..0a56f01 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_port.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_port.c
@@ -139,7 +139,7 @@
 	int i;
 	int offset = next - start;
 
-	for (i = 0; i <= num; i++) {
+	for (i = 0; i < num; i++) {
 		ret += be64_to_cpu(*curr);
 		curr += offset;
 	}