netfilter: arptables: use percpu jumpstack

netfilter: arptables: use percpu jumpstack

commit 00d00e0c31ec ("netfilter: xtables: avoid percpu ruleset duplication")

Unlike ip and ip6tables, arp tables were never converted to use the percpu
jump stack.

It still uses the rule blob to store return address, which isn't safe
anymore since we now share this blob among all processors.

Because there is no TEE support for arptables, we don't need to cope
with reentrancy, so we can use loocal variable to hold stack offset.

Fixes: 00d00e0c31ec ("netfilter: xtables: avoid percpu ruleset duplication")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>