mlx4_core: Remove unused doorbell_lock

struct mlx4_priv.doorbell_lock is never used, so delete it.
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/net/mlx4/main.c

@@ -542,8 +542,6 @@ static int __devinit mlx4_setup_hca(struct mlx4_dev *dev)
 	struct mlx4_priv *priv = mlx4_priv(dev);
 	int err;
 
-	MLX4_INIT_DOORBELL_LOCK(&priv->doorbell_lock);
-
 	err = mlx4_init_uar_table(dev);
 	if (err) {
 		mlx4_err(dev, "Failed to initialize "

drivers/net/mlx4/mlx4.h

@@ -275,7 +275,6 @@ struct mlx4_priv {
 
 	struct mlx4_uar		driver_uar;
 	void __iomem	       *kar;
-	MLX4_DECLARE_DOORBELL_LOCK(doorbell_lock)
 
 	u32			rev_id;
 	char			board_id[MLX4_BOARD_ID_LEN];