ar71xx: add kernel support for BHU Networks BXU2000n-2 A1 board

BXU2000n-2 A1 is a BHU Networks WLAN board, use ar9341 chip.

Patchwork: http://patchwork.openwrt.org/patch/4183/
Signed-off-by: Terry Yang <yangbo@bhunetworks.com>
[juhosg:
- rename and refresh kernel patch,
- fix some checkpatch warnings and adjust whitespaces in
mach-bhu-bxu2000n2-a.c]
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38591 3c298f89-4303-0410-b956-a3cf2f4a3e73