net/mlx4: clean up a type issue

These functions returns type bool, not pointers, so return false instead
of NULL.

Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/52d0814a-7287-4160-94b5-ac7939ac61c6@moroto.mountain
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -294,7 +294,7 @@ static bool check_duplicate_entry(struct mlx4_dev *dev, u8 port,
 	struct mlx4_promisc_qp *dqp, *tmp_dqp;
 
 	if (port < 1 || port > dev->caps.num_ports)
-		return NULL;
+		return false;
 
 	s_steer = &mlx4_priv(dev)->steer[port - 1];
 
@@ -375,7 +375,7 @@ static bool can_remove_steering_entry(struct mlx4_dev *dev, u8 port,
 	bool ret = false;
 
 	if (port < 1 || port > dev->caps.num_ports)
-		return NULL;
+		return false;
 
 	s_steer = &mlx4_priv(dev)->steer[port - 1];