openvswitch: Fix typos in CT headers

These comments hadn't caught up to their implementations, fix them.

Fixes: 7f8a436e "openvswitch: Add conntrack action"
Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>