geneve, specs: Add port range to rt_link specification

geneve, specs: Add port range to rt_link specification

Add the port range to rt_link, example:

  # tools/net/ynl/pyynl/cli.py --spec Documentation/netlink/specs/rt_link.yaml \
    --do getlink --json '{"ifname": "geneve1"}' --output-json | jq
  {
    "ifname": "geneve1",
    [...]
    "linkinfo": {
      "kind": "geneve",
      "data": {
        "id": 1000,
        "remote": "147.28.227.100",
        "udp-csum": 0,
        "ttl": 0,
        "tos": 0,
        "label": 0,
        "df": 0,
        "port": 49431,
        "udp-zero-csum6-rx": 1,
        "ttl-inherit": 0,
        "port-range": {
          "low": 4000,
          "high": 5000
        }
      }
    },
    [...]
  }

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://patch.msgid.link/20250226182030.89440-2-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>