[device/nvidia-bluefield]: Fix brkout mode in platform/vs/docker-sonic-vs/platform-nvda-bf.json (sonic-net#113)

Why I did it
We will use the following command to generate the config_db.json. But the default_brkout_mode should fully equal than what was declared in the platform file, hwsku.json. Otherwise it will raise the following exception.

sonic-cfggen -p /usr/share/sonic/device/x86_64-kvm_x86_64-r0/platform-nvda-bf.json -k Nvidia-MBF2H536C --print-data 
Traceback (most recent call last):
      File "/usr/local/bin/sonic-cfggen", line 454, in <module>
          main()
        File "/usr/local/bin/sonic-cfggen", line 314, in main
          (ports, _, _) = get_port_config(hwsku, platform, args.port_config, asic_id)
        File "/usr/local/lib/python3.7/dist-packages/portconfig.py", line 139, in get_port_config
          return parse_platform_json_file(hwsku_json_file, port_config_file)
        File "/usr/local/lib/python3.7/dist-packages/portconfig.py", line 354, in parse_platform_json_file
          child_ports = get_child_ports(intf, brkout_mode, platform_json_file)
        File "/usr/local/lib/python3.7/dist-packages/portconfig.py", line 327, in get_child_ports
          mode_handler = BreakoutCfg(interface, breakout_mode, port_dict[INTF_KEY][interface])
        File "/usr/local/lib/python3.7/dist-packages/portconfig.py", line 255, in __init__
          raise RuntimeError("Unsupported breakout mode {}!".format(bmode))
      RuntimeError: Unsupported breakout mode 1x100G!
How I did it
Add breakout_modes in platform-nvda-bf.json.

How to verify it
root@850b4902a518:/# sonic-cfggen -p /usr/share/sonic/device/x86_64-kvm_x86_64-r0/platform-nvda-bf.json -k Nvidia-MBF2H536C --print-data
{
    "DEVICE_METADATA": {
        "localhost": {
            "hwsku": "Nvidia-MBF2H536C"
        }
    },
    "PORT": {
        "Ethernet0": {
            "alias": "etp1",
            "lanes": "0,1,2,3",
            "speed": "100000",
            "index": "1"
        },
        "Ethernet4": {
            "alias": "etp2",
            "lanes": "4,5,6,7",
            "speed": "100000",
            "index": "2"
        }
    },
    "BREAKOUT_CFG": {
        "Ethernet0": {
            "brkout_mode": "1x100G"
        },
        "Ethernet4": {
            "brkout_mode": "1x100G"
        }
    }
}

Signed-off-by: Ze Gan <[email protected]>

Author: Pterosaur

platform/vs/docker-sonic-vs/platform-nvda-bf.json

@@ -4,6 +4,7 @@
             "index": "1,1,1,1",
             "lanes": "0,1,2,3",
             "breakout_modes": {
+                "1x100G": ["etp1"],
                 "1x100G[50G,40G,25G,10G]": ["etp1"],
                 "2x50G[25G,10G]": ["etp1a", "etp1b"],
                 "4x10G[25G]": ["etp1a", "etp1b", "etp1c", "etp1d"]
@@ -13,6 +14,7 @@
             "index": "2,2,2,2",
             "lanes": "4,5,6,7",
             "breakout_modes": {
+                "1x100G": ["etp2"],
                 "1x100G[50G,40G,25G,10G]": ["etp2"],
                 "2x50G[25G,10G]": ["etp2a", "etp2b"]
             }