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>

target/linux/ramips/mt7620/base-files/etc/board.d/01_leds

@@ -101,6 +101,7 @@ edimax,br-6478ac-v2|\
 edimax,ew-7478apc)
 	ucidef_set_led_netdev "wifi_led" "wifi" "blue:wlan" "wlan0"
 	;;
+ampedwireless,b1200ex|\
 edimax,ew-7476rpc|\
 edimax,ew-7478ac)
 	ucidef_set_led_switch "lan" "lan" "green:lan"  "switch0" "0x20"

target/linux/ramips/mt7620/base-files/etc/board.d/02_network

@@ -38,6 +38,7 @@ ramips_setup_interfaces()
 			"3:lan" "4:wan" "6@eth0"
 		;;
 	alfa-network,tube-e4g|\
+	ampedwireless,b1200ex|\
 	buffalo,wmr-300|\
 	dlink,dch-m225|\
 	edimax,ew-7476rpc|\