netfilter: hashlimit: do not use indirect calls during gc

commit 28b3a427 upstream.

no need, just use a simple boolean to indicate we want to reap all
entries.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>