UPSTREAM: ip6tables: use match, target and data copy_to_user helpers

Convert ip6tables to copying entries, matches and targets one by one,
using the xt_match_to_user and xt_target_to_user helper functions.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Bug: 120612905
Change-Id: I50db052755301496d318a19444b922bd655866c1
(cherry picked from commit e47ddb2c4691fd2bd8d25745ecb6848408899757)
Signed-off-by: Hridya Valsaraju <hridya@google.com>