ar71xx: add kernel support for DRAGINO2

ar71xx: add kernel support for DRAGINO2

This patch adds support for DRAGINO2 board (used by
Meshpotato v2). Most of the files included can be
found in the official svn repository provided by the
company [1]. I have just adapt it to the last OpenWrt
trunk revision (Fri Oct 4 10:49:47 2013).

 1. http://svn.dragino.com/dragino2

Patchwork: http://patchwork.openwrt.org/patch/4234/
Signed-off-by: Pau Escrich <p4u@dabax.net>
[juhosg:
 - rename and refresh kernel patch,
 - fix checkpatch warnings in  mach-dragino2.c]
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38587 3c298f89-4303-0410-b956-a3cf2f4a3e73