ath79: add support for the Netgear WNDRMAC v1

ath79: add support for the Netgear WNDRMAC v1

The Netgear WNDRMAC v1 is a hardware variant of the Netgear WNDR3700 v2

Specifications
==============
* SoC: Atheros AR7161
* RAM: 64mb
* Flash on board: 16mb
* WiFi: Atheros AR9220 (a/n), Atheros AR9223 (b/g/n)
* Ethernet: RealTek RTL8366SR (1xWAN, 4xLAN, Gigabit)
* Power: 12 VDC, 2.5 A
* Full specs on [openwrt.org](https://openwrt.org/toh/hwdata/netgear/netgear_wndrmac_v1)

Flash Instructions
==================
It is possible to use the OEM Upgrade page to install the `factory`
variant of the firmware.

After the initial upgrade, you will need to telnet into the router
(default IP 192.168.1.1) to install anything. You may install LuCI
this way. At this point, you will have a web interface to configure
OpenWRT on the WNDRMAC v1.

Please use the `sysupgrade` variant for subsequent flashes.

Recovery Instructions
=====================
A TFTP-based recovery flash is possible if the need arises. Please refer
to the WNDR3700 page on openwrt.org for details.

https://openwrt.org/toh/netgear/wndr3700#troubleshooting_and_recovery

Signed-off-by: Renaud Lepage <root@cybikbase.com>
[update DTSI include name]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>