netfilter: remove last traces of variable-sized extensions

get rid of the (now unused) nf_ct_ext_add_length define and also
rename the function to plain nf_ct_ext_add().

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2 files changed