tc: pedit: Support JSON dumping

tc: pedit: Support JSON dumping

The action pedit does not currently support dumping to JSON. Convert
print_pedit() to the print_* family of functions so that dumping is correct
both in plain and JSON mode. In plain mode, the output is character for
character the same as it was before. In JSON mode, this is an example dump:

$ tc filter add dev dummy0 ingress prio 125 flower \
         action pedit ex munge udp dport set 12345 \
	                 munge ip ttl add 1        \
			 munge offset 10 u8 clear
$ tc -j filter show dev dummy0 ingress | jq
[
  {
    "protocol": "all",
    "pref": 125,
    "kind": "flower",
    "chain": 0
  },
  {
    "protocol": "all",
    "pref": 125,
    "kind": "flower",
    "chain": 0,
    "options": {
      "handle": 1,
      "keys": {},
      "not_in_hw": true,
      "actions": [
        {
          "order": 1,
          "kind": "pedit",
          "control_action": {
            "type": "pass"
          },
          "nkeys": 3,
          "index": 1,
          "ref": 1,
          "bind": 1,
          "keys": [
            {
              "htype": "udp",
              "offset": 0,
              "cmd": "set",
              "val": "3039",
              "mask": "ffff0000"
            },
            {
              "htype": "ipv4",
              "offset": 8,
              "cmd": "add",
              "val": "1000000",
              "mask": "ffffff"
            },
            {
              "htype": "network",
              "offset": 8,
              "cmd": "set",
              "val": "0",
              "mask": "ffff00ff"
            }
          ]
        }
      ]
    }
  }
]

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