dtoc: Drop sys.exit() in test_fdt

This breaks using pytest to run the tests. Drop it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/dtoc/test_fdt.py b/tools/dtoc/test_fdt.py
index 8a990b8..a3e36ea 100755
--- a/tools/dtoc/test_fdt.py
+++ b/tools/dtoc/test_fdt.py
@@ -851,4 +851,3 @@
 
 if __name__ == '__main__':
     sys.exit(main())
-sys.exit(1)