cleanup - config_item_int16() & DEFAULT_IPV4_LOCAL_PREFIXLEN am: 6be24d8214 am: e4e1e3292d

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/android-clat/+/11736254

Change-Id: Ia506f1d196fbef1cbe31bc4722415b093ad8926b