rdma: Add resource tracking summary

$ rdma res
1: mlx5_0: curr/max: pd 3/16777216 cq 5/16777216 qp 4/262144
2: mlx5_1: curr/max: pd 3/16777216 cq 5/16777216 qp 4/262144
3: mlx5_2: curr/max: pd 3/16777216 cq 5/16777216 qp 4/262144
4: mlx5_3: curr/max: pd 2/16777216 cq 3/16777216 qp 2/262144
5: mlx5_4: curr/max: pd 3/16777216 cq 5/16777216 qp 4/262144

$ rdma res show mlx5_4
5: mlx5_4: curr/max: pd 3/16777216 cq 5/16777216 qp 4/262144

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>