netfilter: nft_dynset: fix timeout updates on 32bit

This must now use a 64bit jiffies value, else we set
a bogus timeout on 32bit.

Fixes: 8e1102d5 ("netfilter: nf_tables: support timeouts larger than 23 days")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>