IB/mlx5: Remove unused code in mr.c

The variable start in struct mlx5_ib_mr is never used. Remove it.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx5/mlx5_ib.h

@@ -264,7 +264,6 @@ struct mlx5_ib_mr {
 	enum ib_wc_status	status;
 	struct mlx5_ib_dev     *dev;
 	struct mlx5_create_mkey_mbox_out out;
-	unsigned long		start;
 };
 
 struct mlx5_ib_fast_reg_page_list {