ramips: add support for Amped Wireless B1200EX

ramips: add support for Amped Wireless B1200EX

This device is almost identical to the already supported Edimax
EW-7476RP5, the only differences are:
- There is no mode selection slider switch on this device
- The two wireless LEDs are green instead of blue
- Model name in the CSYS header is RN10

Additional changes:
- Moved WiFi LEDs and the slider switch to the individual dt files
- Added ieee80211-freq-limit to the mt7612e radio to properly disable
  2.4GHz band on this radio

Device specifications:
SoC:	MediaTek MT7620a @ 580MHz
RAM:	64M (Winbond W9751G6KB-25)
FLASH:	8MB (Macronix)
WiFi:	SoC-integrated: MediaTek MT7620a bgn
WiFi:	MediaTek MT7612EN nac
GbE:	1x (RTL8211E)
BTN:	WPS/RESET
LED:	- WiFi 5G (green)
	- WiFi 2.4G (green)
	- Signal Strength (green)
	- Power (green)
	- WPS (green)
	- LAN (green)
UART:	UART is present as Pads with throughholes on the PCB. They are
	located next to the WPS button
	3.3V - RX - GND - TX / 57600-8N1
	3.3V is the square pad

Installation:
Upload the sysupgrade image via the default web interface

Signed-off-by: Daniel Fuchs <software@sagacioussuricata.com>