brcm47xx: Add support for Huawei E970

This patch adds support for Huawei E970 wireless gateway devices.
It has been tested on an E970 labelled as T-Mobile web'n'walk Box IV.
E960/B970 should work too, from what I know it's basically the same hardware.

The device has a Broadcom BCM5354 SoC and a built-in 3G USB modem.

It uses a hardware watchdog which needs GPIO-7 to be toggled at least
every 1-2 seconds. This patch uses gpio_wdt module (see my previous
patch today) to take care of this.

Tested and works:  3G wan,  wlan+LED,  VLAN config,  failsafe using reset
button,   image to be used for upgrade from OEM firmware's web interface

Link to the wiki page I've created:  <http://wiki.openwrt.org/toh/huawei/e970

>

Issue:

* lzma-loader crashes, so gzipped kernel is used. Presumably due to watchdog
  reset during kernel decompress.

Signed-off-by: Mathias Adam <m.adam--openwrt@adamis.de>

SVN-Revision: 38011