genxml: pack: deal with default field not being simple integers

Storing integers into enums doesn't seem to cause issues in C, but
with our builder tests written in C++ this causes warnings/errors.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4938>

src/intel/genxml/gen_pack_header.py

@@ -617,7 +617,13 @@ class Parser(object):
                 continue
             if field.default is None:
                 continue
-            default_fields.append("   .%-35s = %6d" % (field.name, field.default))
+
+            if field.is_builtin_type():
+                default_fields.append("   .%-35s = %6d" % (field.name, field.default))
+            else:
+                # Default values should not apply to structures
+                assert field.is_enum_type()
+                default_fields.append("   .%-35s = (enum %s) %6d" % (field.name, self.gen_prefix(safe_name(field.type)), field.default))
 
         if default_fields:
             print('#define %-40s\\' % (self.gen_prefix(name + '_header')))