netfilter: conntrack: avoid excess memory allocation

This is now a fixed-size extension, so we don't need to pass a variable
alloc size. This (harmless) error results in allocating 32 instead of
the needed 16 bytes for this extension as the size gets passed twice.

Fixes: 23014011ba420 ("netfilter: conntrack: support a fixed size of 128 distinct labels")
Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/net/netfilter/nf_conntrack_labels.h

···
 	if (net->ct.labels_used == 0)
 		return NULL;
 
-	return nf_ct_ext_add_length(ct, NF_CT_EXT_LABELS,
-				    sizeof(struct nf_conn_labels), GFP_ATOMIC);
+	return nf_ct_ext_add(ct, NF_CT_EXT_LABELS, GFP_ATOMIC);
 #else
 	return NULL;
 #endif