drm/i915/selftests: Setup engine->retire for mock_engine

Enable and cleanup the engine->retire for the mock engine.

Fixes: dc93c9b6 ("drm/i915/gt: Schedule request retirement when signaler idles")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191221001136.720154-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/mock_engine.c

@@ -290,6 +290,7 @@ int mock_engine_init(struct intel_engine_cs *engine)
 	intel_engine_init_breadcrumbs(engine);
 	intel_engine_init_execlists(engine);
 	intel_engine_init__pm(engine);
+	intel_engine_init_retire(engine);
 	intel_engine_pool_init(&engine->pool);
 
 	ce = create_kernel_context(engine);
@@ -332,6 +333,7 @@ void mock_engine_free(struct intel_engine_cs *engine)
 	intel_context_unpin(engine->kernel_context);
 	intel_context_put(engine->kernel_context);
 
+	intel_engine_fini_retire(engine);
 	intel_engine_fini_breadcrumbs(engine);
 
 	kfree(engine);