net/mlx5: Add command failures data to debugfs

Add new counters to command interface debugfs to count command failures.
The following counters added:
total_failed - number of times command failed (any kind of failure).
failed_mbox_status - number of times command failed on bad status
returned by FW.

In addition, add data about last command failure to command interface
debugfs:
last_failed_errno - last command failed returned errno.
last_failed_mbox_status - last bad status returned by FW.

Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>