iris: Fix assigning the output handle for exporting for KMS

Fixes gbm_bo_get_handle() used for KMS in glamor.

src/gallium/drivers/iris/iris_resource.c

@@ -498,7 +498,8 @@ iris_resource_get_handle(struct pipe_screen *pscreen,
    case WINSYS_HANDLE_TYPE_SHARED:
       return iris_bo_flink(res->bo, &whandle->handle) == 0;
    case WINSYS_HANDLE_TYPE_KMS:
-      return iris_bo_export_gem_handle(res->bo) != 0;
+      whandle->handle = iris_bo_export_gem_handle(res->bo);
+      return true;
    case WINSYS_HANDLE_TYPE_FD:
       return iris_bo_export_dmabuf(res->bo, (int *) &whandle->handle) == 0;
    }