The hardware should be almost the same as TL-WR720N-v3.  WiFi and LAN networks
were tested by "Lo Yuk Fai <loyukfai@gmail.com>".  Failsafe and slider switch
were tested by "Wong min <alpha080@gmail.com>".
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

Backport of r46046

git-svn-id: svn://svn.openwrt.org/openwrt/branches/chaos_calmer@46056 3c298f89-4303-0410-b956-a3cf2f4a3e73