arptables: Fix opcode printing in numeric output

This line of code was dropped by accident, add it back.

Fixes: 68e5e18210b8d ("nft-arp: adds nft_arp_save_firewall")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>
1 file changed