xtables-addons: disable for kernel 4.1 for now

Netfilter APIs have changed, so the code requuires updates to compile
successfully.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46111 3c298f89-4303-0410-b956-a3cf2f4a3e73