ebtables: use match, target and data copy_to_user helpers

Convert ebtables to copying entries, matches and targets one by one.

The solution is analogous to that of generic xt_(match|target)_to_user
helpers, but is applied to different structs.

Convert existing helpers ebt_make_XXXname helpers that overwrite
fields of an already copy_to_user'd struct with ebt_XXX_to_user
helpers that copy all relevant fields of the struct from scratch.

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