net/mlx5_en: Add missing check for memory allocation failure

The patch afb736e9330a: "net/mlx5: Ethernet resource handling files"
from May 28, 2015, leads to the following static checker warning:

drivers/net/ethernet/mellanox/mlx5/core/en_flow_table.c:726 mlx5e_create_main_flow_table()
error: potential null dereference 'g'.  (kcalloc returns null)

Fixes: afb736e9330a ("net/mlx5: Ethernet resource handling files")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx5/core/en_flow_table.c

@@ -722,6 +722,8 @@ static int mlx5e_create_main_flow_table(struct mlx5e_priv *priv)
 	u8 *dmac;
 
 	g = kcalloc(9, sizeof(*g), GFP_KERNEL);
+	if (!g)
+		return -ENOMEM;
 
 	g[0].log_sz = 2;
 	g[0].match_criteria_enable = MLX5_MATCH_OUTER_HEADERS;