netfilter: remove use of obsolete compatibility config symbols for mark and connmark

fixes duplication of xt_mark and xt_connmark module entries

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37344 3c298f89-4303-0410-b956-a3cf2f4a3e73