[NETFILTER]: fix ifdef for connmark support in nf_conntrack_netlink

When ctnetlink was ported from ip_conntrack to nf_conntrack two #ifdef's
for connmark support were left unchanged and this code was never
compiled.

Problem noticed by Daniel De Graaf.

Signed-off-by: Martin Josefsson <gandalf@wlug.westbo.se>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>