net/mlx4_core: Set correctly allow_loopback flag

The allow_loopback flag was wrongly set using arithmetic bit operation, change
the code to use logical bit operation.
Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/mcg.c

@@ -1157,7 +1157,7 @@ int mlx4_multicast_attach(struct mlx4_dev *dev, struct mlx4_qp *qp, u8 gid[16],
 			.priority = MLX4_DOMAIN_NIC,
 		};
 
-		rule.allow_loopback = ~block_mcast_loopback;
+		rule.allow_loopback = !block_mcast_loopback;
 		rule.port = port;
 		rule.qpn = qp->qpn;
 		INIT_LIST_HEAD(&rule.list);