netfilter: ebtables: add ebt_free_table_info function

A ebt_free_table_info frees all of chainstacks.
It similar to xt_free_table_info. this inline function
reduces code line.

Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>