sdbus++: events: fix Redfish registry type for enums

Fix two issues with the Redfish registry generation:
    1. Enums should be strings (and not numbers) in the MessageArgs.
    2. Enums have a complex type which requires do a "type_tuple"
       processing before attempting to look up the Registry type.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ieda935f553dd73a22eedbe9ab87f0950554b95a2
diff --git a/tools/sdbusplus/property.py b/tools/sdbusplus/property.py
index c1b24bb..7d52b2f 100644
--- a/tools/sdbusplus/property.py
+++ b/tools/sdbusplus/property.py
@@ -257,14 +257,14 @@
         "enum": {
             "cppName": "enum",
             "params": 1,
-            "registryName": "number",
+            "registryName": "string",
         },
     }
 
     """ Get the registry type of the property. """
 
     def registry_type(self):
-        return Property.propertyMap[self.typeName]["registryName"]
+        return Property.propertyMap[self.__type_tuple()[0]]["registryName"]
 
     """ Take a list of dbus types and perform validity checking, such as:
             [ variant [ dict [ int32, int32 ], double ] ]