'default false' should be 'default n', though they happen to have the
same effect here, due to undefined symbols ('false' in this case)
evaluating to n in a tristate sense.
Remove the default instead of changing it. bool and tristate symbols
implicitly default to n.
Discovered with the
https://github.com/ulfalizer/Kconfiglib/blob/master/examples/list_undefined.py
script.