Adds iptables/netfilter kernel modules for Amlogic

This PR adds basic modules for iptables/netfilter.The modules are the same as in mainstream OpenElec - only IPv6 stuff is not included as IPv6 is not enabled in the kernel.
I have tested it on my M8, which is connected directly to ISP network on eth0 (for IPTV) and to my home network on WIFI. Therefore; I enabled this to restrict access to the device from outside...