ramips: add support for Edimax EW-7476RPC / EW-7478AC

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 - RFKILL/RF 50%/RF 100% toggle
LED:	- Wifi 5g (blue)
	- Wifi 2g (blue)
	- Crossband (green)
	- Power (green)
	- WPS (green)
	- LAN (Green)
UART:	UART is present as Pads with throughholes on the PCB. They are
	located next to the switch for the wifi configuration
	3.3V - RX - GND - TX / 57600-8N1
	3.3V is the square pad

Installation
------------
Update the factory image via the web-interfaces (by default:
192.168.9.2/24).
http://192.168.9.2/index.asp

ramips: add Edimax EW-7478AC

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 - RFKILL/RF 50%/RF 100% toggle
LED:	- Wifi 5g (blue)
	- Wifi 2g (blue)
	- Crossband (green)
	- Power (green)
	- WPS (green)
	- LAN (Green)
UART:	UART is present as Pads with throughholes on the PCB. They are
	located next to the switch for the wifi configuration
	3.3V - RX - GND - TX / 57600-8N1
	3.3V is the square pad

Installation
------------
Update the factory image via the web-interfaces (by default:
http://edimaxext.setup

)
Or push wpa button on power on and send firmware via tftp to 192.168.1.6

The EW-7478AC is identical to the EW-7476RPC, except instead of 2 internal
antennas it has 2 external ones.

Signed-off-by: Birger Koblitz <mail@birger-koblitz.de>
[merge conflict in 01_leds]
Signed-off-by: Petr Štetiar <ynezz@true.cz>