ar71xx: add kernel support for Netgear WNR2200 wireless router

ar71xx: add kernel support for Netgear WNR2200 wireless router

This patch adds OpenWRT support for the Netgear WNR2200 (N300)
wireless router with USB.

Technical details of this router can be found at
http://www.netgear.com/home/products/wirelessrouters/work-and-play/WNR2200.aspx
and http://wikidevi.com/wiki/Netgear_WNR2200

Signed-off-by: Aidan Kissane <aidankissane@googlemail.com>
Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>
Patchwork: http://patchwork.openwrt.org/patch/4055/
[juhosg:
  - add commit message and SoB line from the original patch
  - remove dead code from mach-wnr2200.c
  - refresh 624-MIPS-ath79-WNR2200-support.patch]
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38059 3c298f89-4303-0410-b956-a3cf2f4a3e73