nft: fix syntax error in nft_parse_cmp()

This fixes a syntax error, remove ; in an if statement

Signed-off-by: Giuseppe Longo <giuseppelng@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
nft-ipv46: replace offset var with ctx->payload.offset

The offset variable (undefined) is passed to DEBUGP function,
so you get a compilation error if you try to build iptables
with debug enabled

Signed-off-by: Giuseppe Longo <giuseppelng@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>