netlink: off-by-one write in netdev chain device array

netlink: off-by-one write in netdev chain device array

==728473== Invalid write of size 8
==728473==    at 0x48960F2: netlink_delinearize_chain (netlink.c:422)
==728473==    by 0x4896252: list_chain_cb (netlink.c:459)
==728473==    by 0x4896252: list_chain_cb (netlink.c:441)
==728473==    by 0x4F2C654: nftnl_chain_list_foreach (chain.c:1011)
==728473==    by 0x489629F: netlink_list_chains (netlink.c:478)
==728473==    by 0x4882303: cache_init_objects (rule.c:177)
==728473==    by 0x4882303: cache_init (rule.c:222)
==728473==    by 0x4882303: cache_update (rule.c:272)
==728473==    by 0x48A7DCE: nft_evaluate (libnftables.c:408)
==728473==    by 0x48A86D9: nft_run_cmd_from_buffer (libnftables.c:449)
==728473==    by 0x10A5D6: main (main.c:338)

Fixes: 3fdc7541fba0 ("src: add multidevice support for netdev chain")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>