tc: Add support for ETS Qdisc

tc: Add support for ETS Qdisc

Add a new module to generate and parse options specific to the ETS Qdisc.

Example output:

    bands 8 strict 3 priomap 0 1 2 3 4 5 6 7
qdisc ets 1: root refcnt 2 offloaded bands 8 strict 3 quanta 1514 1514 1514 1514 1514 priomap 0 1 2 3 4 5 6 7 7 7 7 7 7 7 7 7
[
  {
    "kind": "ets",
    "handle": "1:",
    "root": true,
    "refcnt": 2,
    "offloaded": true,
    "options": {
      "bands": 8,
      "strict": 3,
      "quanta": [1514, 1514, 1514, 1514, 1514],
      "priomap": [0, 1, 2, 3, 4, 5, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7]
    }
  }
]

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>