#79 Upstream ath71xx-ath79 modernization efforts.

Upstream seems to be ramping up efforts to modernize atheros boards. https://openwrt.org/docs/techref/targets/ar71xx-ath79 https://openwrt.org/docs/techref/targets/ath79 https://lists.openwrt.org/pipermail/openwrt-devel/2018-February/011312.html https://git.openwrt.org/?p=openwrt/openwrt.git&a=search&h=HEAD&st=commit&s=ath79: https://forum.openwrt.org/t/porting-guide-ar71xx-to-ath79/13013 https://forum.openwrt.org/t/ath79-target-status/18614

Yes, I have been watching it for quite a while now and I'm glad that they started down this path almost a year ago. The plan has been to move all supported ar71xx targets to use ath79 in v1.5.x once it is a little bit more stable.