ANDROID: GKI: add Android ABI padding to struct nf_conn

Try to mitigate potential future driver core api changes by adding
padding to struct nf_conn;

Bug: 151154716
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ib18a9a929d351c66556f1f27b217cbf22b733a10