lantiq: add basic support for AVM FRITZ!Box 3390

lantiq: add basic support for AVM FRITZ!Box 3390

The FRITZ!Box 3390 actually contains two SoCs, one Lantiq with a
5GHz WiFi and one AR9342 with a 2.4GHz WiFi. Only the Lantiq
has access to the flash memory, the Atheros runs fully from RAM.

Specifications
--------------

  - Lantiq 500 MHz
  - 128MiB RAM
  - 128MiB NAND
  - 256k Flash
  - AR9580 5GHz WiFi
  - AR9342 560 MHz
  - 64MiB RAM
  - AR9328 2.4GHz WiFi

Remarks
-------

This commit only adds support for the Lantiq side of things and
prepares the drivers for communication with the Atheros SoC. Thus,
only 5GHz WiFi works by default, the 2.4GHz WiFi will be added via
another target.

Some kernel patches will be required to add support for the Atheros SoC.

Installation
------------

Use the eva_ramboot.py script to boot the initramfs image. Then, transfer
the sysupgrade image to the device and run sysupgrade to flash it to the
NAND.

Signed-off-by: Andreas Böhler <dev@aboehler.at>
Acked-by: Aleksander Jan Bajkowski A.Bajkowski@stud.elka.pw.edu.pl
Signed-off-by: Joachim Cerny <cocktail_yogi@web.de>