netfilter: ebtables: remove BUGPRINT messages

They are however frequently triggered by syzkaller, so remove them.

ebtables userspace should never trigger any of these, so there is little
value in making them pr_debug (or ratelimited).
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>