ramips: add support for Asus RT-N10P V3 / RT-N11P B1 / RT-N12 VP B1

ramips: add support for Asus RT-N10P V3 / RT-N11P B1 / RT-N12 VP B1

Specifications:

- MT7628NN @ 580 MHz
- 32 MB RAM
- 8 MB Flash
- 5x 10/100 Mbps Ethernet (built-in switch)
- 2.4 GHz WLAN
- 2x external, non-detachable antennas (1x for RT-N10P V3)

Flash instructions:

1. Set PC network interface to 192.168.1.75/24.
2. Connect PC to the router via LAN.
3. Turn router off, press and hold reset button, then turn it on.
4. Keep the button pressed till power led starts to blink.
5. Upload the firmware file via TFTP. (Any filename is accepted.)
6. Wait until the router reboots.

Signed-off-by: Ernst Spielmann <endspiel@disroot.org>
[fix node/property name for state_default]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>