ar8327: add IGMP Snooping support
This add support for IGMP Snooping on atheros switches (disabled by default),
which avoids flooding the network with multicast data.
Tested on TL-WDR4300: disabling IGMP Snooping results in multicast flooding
on each specific port, enabling it back again prevents each port from
receiving all multicast packets.
Partially based on: http://patchwork.ozlabs.org/patch/418122/
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@48268
3c298f89-4303-0410-b956-
a3cf2f4a3e73