ramips: add support for D-Link DAP-1325-A1

ramips: add support for D-Link DAP-1325-A1

This patch adds support for D-Link DAP-1325-A1 (Range Extender Wi-Fi N300)

Specifications:
- SoC: 580Mhz MT7628NN
- RAM: 64MB, DDR2 SDRAM
- Storage: 8MB, SPI (W25Q64JVSSIQ)
- Ethernet: 1x 10/100 LAN port
- WIFI: 2.4 GHz 802.11bgn
- LED: Status (2x to provide 3 colors), Wi-Fi Signal Strength (4x)
- Buttons: Reset, WPS
- UART: Serial console (57600, 8n1)
Row of 4 holes near LAN port, starting from square hole:
3.3V, TX,RX,GND
- FCC ID: fccid.io/KA2AP1325A1/

Installation:

Failsafe UI
Firmware can be uploaded with Failsafe UI web page:
- turn device off
- press and hold reset button
- turn device on
- keep holding reset until red wifi strength led turns on (ab. 10sec)
- connect to device through LAN port
PC must be configured with static ip (192.168.0.x)
- connect to 192.168.0.50
- select image to be flashed and upload.
Device will reboot after successful update

Serial port/TFTP server
- Connect through serial connectors on PCB (e.g. with teraterm)
- Set up a TFTP server, and connect through LAN with static IP
- Put image file in the root of the server
- Boot the device and select '2' at U-Boot startup
- Set device IP, server IP and image file name
- Start upload and flash

Signed-off-by: Giovanni Cascione <ing.cascione@gmail.com>
[fix whitespaces in DTS, convert to nvmem, add mtd-eeprom]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>