ramips: add gpio pin 72 in mt7620 chips to dtsi files

describes register set to control last gpio pin on mt7620 platfrom

Signed-off-by: Pavel Löbl <lobl.pavel@gmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39162 3c298f89-4303-0410-b956-a3cf2f4a3e73
ramips: add support for RT-N14U (mt7620n based) board

added dts file and userspace scripts modified to support Asus RT-N14U board

current support status:
usb        works
ethernet   works
buttons    reset, wps
leds       asus:blue:[usb|lan|wan|air|power]
i2c        not tested
uart       not tested
wifi       not yet

Signed-off-by: Pavel Löbl <lobl.pavel@gmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39163 3c298f89-4303-0410-b956-a3cf2f4a3e73