This PR adds support for TP-Link TL-WR842N-v2 router which is supported by ar71xx to ath79.

This is a low cost model with following specs:

CPU: Atheros AR9341 SoC
RAM: 32 MB DDR1
Flash: 8 MB NOR SPI
Switch: Internal AR9341 5 port 10/100 Mbit
Ports:  5x 10/100 Mbit(1x WAN, 4x LAN)
USB: 1x USB2.0
WLAN: 2.4 GHZ AR9341

Installation:

Simply flash the factory image through stock firmware WEB UI.

Signed-off-by: Robert Marko <robimarko@gmail.com>