firmware-utils/mktplinkfw: add support for the TL-MR3220 v2

Based on the following patch:
http://patchwork.openwrt.org/patch/3043/



Signed-off-by: Cezary Jackiewicz <cezary.jackiewicz@gmail.com>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 34781