ath79: add support for Teltonika RUT230 v1

ath79: add support for Teltonika RUT230 v1

This commit adds support for the Teltonika RUT230 v1, a Atheros AR9331
based router with a Quectel UC20 UMTS modem.

Hardware
--------
Atheros AR9331
16 MB SPI-NOR XTX XT25F128B
64M DDR2 memory
Atheros AR9331 1T1R 802.11bgn Wireless
Boootloader: pepe2k U-Boot mod

Hardware-Revision
-----------------
There are two board revisions of the RUT230, a v0 and v1.

A HW version is silkscreened on the top of the PCBs front side as well
as shown in the Teltonika UI. However, this looks to be a different
identifier, as the GPl dump shows this silkscreened / UI shown version
are internally treated identically.

Th following mapping has been obtained from the latest GPl dump.

HW Ver   01 - 04 --> v0
HW Ver > 05      --> v1

My board was a HW Ver 09 and is treated as a v1.

Installation
------------
While attaching power, hold down the reset button and release it after
the signal LEDs flashed 3 times.

Attach your Computer with the devices LAN port and assign yourself the
IPv4 address 192.168.1.10/24. Open a web browser, navigate to
192.168.1.1. Upload the OpenWrt factory image.

The device will install OpenWrt and automatically reboots afterwards.

You can use the smae procedure with the stock firmware to return back to
the vendor firmware.

Signed-off-by: David Bauer <mail@david-bauer.net>