extensions: libxt_cpu: Add translation to nft

extensions: libxt_cpu: Add translation to nft

Add translation for module cpu to nftables.

Examples:

$ sudo iptables-translate -A INPUT -p tcp --dport 80 -m cpu --cpu 0 -j ACCEPT
nft add rule ip filter INPUT tcp dport 80 cpu 0 counter accept

$ sudo iptables-translate -A INPUT -p tcp --dport 80 -m cpu ! --cpu 1 -j ACCEPT
nft add rule ip filter INPUT tcp dport 80 cpu != 1 counter accept

Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>