[NETFILTER]: Fix CONNMARK Kconfig dependency

Connection mark tracking support is one of the feature in connection
tracking, so IP_NF_CONNTRACK_MARK depends on IP_NF_CONNTRACK.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>