configure: remove top restriction

configure.py

diff --git a/configure.py b/configure.py
index 9730dd4..28a784c 100755
--- a/configure.py
+++ b/configure.py
@@ -178,6 +178,5 @@
         config = load_yaml(args.yaml)
         source_files = get_project_source(config)
         top_module = get_top_module(config)
-        assert top_module != 'top'
         io_ranges = get_io_ranges(config)
         write_user_config(top_module, source_files, io_ranges)