RDMA/mlx5: Introduce ODP prefetch counter

For debugging purpose it will be easier to understand if prefetch works
okay if it has its own counter. Introduce ODP prefetch counter and count
per MR the total number of prefetched pages.

In addition remove comment which is not relevant anymore and anyway not in
the correct place.

Link: https://lore.kernel.org/r/20200621104147.53795-1-leon@kernel.org
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/mlx5/restrack.c

@@ -99,6 +99,9 @@ int mlx5_ib_fill_stat_mr_entry(struct sk_buff *msg,
 		    msg, "page_invalidations",
 		    atomic64_read(&mr->odp_stats.invalidations)))
 		goto err_table;
+	if (rdma_nl_stat_hwcounter_entry(msg, "page_prefetch",
+					 atomic64_read(&mr->odp_stats.prefetch)))
+		goto err_table;
 
 	nla_nest_end(msg, table_attr);
 	return 0;