net/mlx4_en: Fix off-by-one in ethtool statistics display

NUM_PORT_STATS was 9 instead of 10, which caused off-by-one bug when
displaying the statistics starting from tx_chksum_offload in ethtool.

Fixes: f8c6455bb04b ('net/mlx4_en: Extend checksum offloading by CHECKSUM COMPLETE')
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/mlx4_en.h

@@ -453,7 +453,7 @@ struct mlx4_en_port_stats {
 	unsigned long rx_chksum_none;
 	unsigned long rx_chksum_complete;
 	unsigned long tx_chksum_offload;
-#define NUM_PORT_STATS		9
+#define NUM_PORT_STATS		10
 };
 
 struct mlx4_en_perf_stats {