net/mlx5_core: Check the return bitmask when querying ISSI

The determination of the supported ISSI versions should be conditioned
on the returned mask, and not only on the return status of the query
ISSI command, fix that.
Signed-off-by: NHaggai Abramovsky <hagaya@mellanox.com>
Signed-off-by: NMajd Dibbiny <majd@mellanox.com>
Signed-off-by: NOr Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -654,7 +654,7 @@ static int mlx5_core_set_issi(struct mlx5_core_dev *dev)
 		dev->issi = 1;
 
 		return 0;
-	} else if (sup_issi & (1 << 0)) {
+	} else if (sup_issi & (1 << 0) || !sup_issi) {
 		return 0;
 	}