Convert C output params to Kotlin return type for void methods.

Previously the signal used was 'status' returning methods (where
failed status is converted to an exception).

New methods have been added to the IDL that don't fit this pattern
and have no return type.

Test: Manual
Change-Id: I5a245d5832bcd4d480707f6a69199b156e89b4fd
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/210500
Reviewed-by: Alex Benton <bentonian@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jim Blackler <jimblackler@google.com>
diff --git a/generator/dawn_json_generator.py b/generator/dawn_json_generator.py
index e2b3bdb..2e11159 100644
--- a/generator/dawn_json_generator.py
+++ b/generator/dawn_json_generator.py
@@ -742,7 +742,7 @@
                     container_type = deepcopy(argument)
                     container_type.length = 'size_t'
                     return container_type
-                if (method.return_type.name.get() == 'status'
+                if (method.return_type.name.get() in ['status', 'void']
                         and argument.type.category == 'structure'):
                     return argument