Added cisco config platform commands

Signed-off-by: Yucai Gu <yucgu@cisco.com>

tests/config_test.py

@@ -1605,7 +1605,7 @@ def setup_class(cls):
 
     def test_config_platform(self, ctx, get_cmd_module, setup_single_cisco_asic):
             expected_output = "cisco"
-            config(ctx)
+            config.main.config(ctx)
             runner = CliRunner()
             result = runner.invoke(config.config.commands["platform"], ['--help'])