kunit: tool: Fix a python tuple typing error

The first argument to namedtuple() should match the name of the type,
which wasn't the case for KconfigEntryBase.

Fixing this is enough to make mypy show no python typing errors again.

Fixes 97752c39

 ("kunit: kunit_tool: Allow .kunitconfig to disable config items")
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Daniel Latypov <dlatypov@google.com>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>