net/mlx5: Add debugfs counters for page commands failures

Add the following new debugfs counters for debug and verbosity:
fw_pages_alloc_failed - number of pages FW requested but driver failed
to allocate.
give_pages_dropped - number of pages given to FW, but command give pages
failed by FW.
reclaim_pages_discard - number of pages which were about to reclaim back
and FW failed the command.

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