iptables: xtables-eb: Remove const qualifier from struct option

iptables: xtables-eb: Remove const qualifier from struct option

As opts is reassigned multiple times, it cannot be made constant.
So remove const qualifier from structure option. This patch fixes the
following warning.

xtables-eb.c: In function ‘ebt_load_match_extensions’:
xtables-eb.c:653:7: warning: assignment discards ‘const’ qualifier
from pointer target type
  opts = ebt_original_options;

Signed-off-by: Varsha Rao <rvarsha016@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>