[Midnightbsd-cvs] [MidnightBSD/src] 7f2989: Fix broken MLX5_IB_INDEX() macro in mlx5ib(4).

[Lucas Holt]

  Branch: refs/heads/master
  Home:   https://github.com/MidnightBSD/src
  Commit: 7f2989a6c0069c8bc02c77949498220e2f34e139
      https://github.com/MidnightBSD/src/commit/7f2989a6c0069c8bc02c77949498220e2f34e139
  Author: Lucas Holt <luke at foolishgames.com>
  Date:   2020-11-15 (Sun, 15 Nov 2020)

  Changed paths:
    M sys/dev/mlx5/mlx5_ib/mlx5_ib.h
    M sys/dev/mlx5/mlx5_ib/mlx5_ib_cong.c

  Log Message:
  -----------
  Fix broken MLX5_IB_INDEX() macro in mlx5ib(4).

The index should be computed as distance from arg[0] and not
the beginning of struct mlx5_ib_congestion .

While at it fix a use of zero length array to avoid depending
on undefined compiler behaviour.