ar71xx: add TP-LINK TL-MR10U

Small router with 4MB flash, 32MB RAM
http://www.tp-link.com.cn/product_300.html



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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36722 3c298f89-4303-0410-b956-a3cf2f4a3e73