drm/nouveau/perfmon: do not forget to destroy the engine context

This fixes a crash when we reload Nouveau DRM.
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/engine/perfmon/base.c

@@ -303,6 +303,7 @@ nouveau_perfctx_dtor(struct nouveau_object *object)
 {
 	struct nouveau_perfmon *ppm = (void *)object->engine;
 	mutex_lock(&nv_subdev(ppm)->mutex);
+	nouveau_engctx_destroy(&ppm->context->base);
 	ppm->context = NULL;
 	mutex_unlock(&nv_subdev(ppm)->mutex);
 }