netfilter: enable CONFIG_NF_CONNTRACK_MARK from kmod-nf-conntrack

Unconditionally enable connmark support and tie it to the conntrack core
module to allow removing this kernel configuration dependency from the
xtables-addons package.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

package/kernel/linux/modules/netfilter.mk

@@ -68,6 +68,7 @@ define KernelPackage/nf-conntrack
   KCONFIG:= \
         CONFIG_NETFILTER=y \
         CONFIG_NETFILTER_ADVANCED=y \
+        CONFIG_NF_CONNTRACK_MARK=y \
         CONFIG_NF_CONNTRACK_ZONES=y \
 	$(KCONFIG_NF_CONNTRACK)
   FILES:=$(foreach mod,$(NF_CONNTRACK-m),$(LINUX_DIR)/net/$(mod).ko)