ath79: port buffalo WZR-450HP2 from ar71xx

ath79: port buffalo WZR-450HP2 from ar71xx

Referencing commit a1837135e04b

Hardware
--------
SoC:	Qualcomm Atheros QCA9558
RAM:	128M DDR2 (Nanya NT5TU64M16HG-AC)
FLASH:	128M SPI-NAND (Spansion S34ML01G100TFI00)
WLAN:	QCA9558 3T3R 802.11 bgn
ETH:	Qualcomm Atheros QCA8337
UART:	115200 8n1
BUTTON:	Reset - WPS - "Router" switch
LED:	2x system-LED, 2x wlan-LED, 1x internet-LED,
	2x routing-LED
	LEDs besides the ethernet ports are controlled
	by the ethernet switch

MAC Address:
 use		address(sample 1)	source
 label		cc:e1:d5:xx:xx:ed	art@macaddr_wan
 lan		cc:e1:d5:xx:xx:ec	art@macaddr_lan
 wan		cc:e1:d5:xx:xx:ed	$label
 WiFi4_2G	cc:e1:d5:xx:xx:ec	art@cal_ath9k

Installation from Serial Console
------------

1. Connect to the serial console. Power up the device and interrupt
   autoboot when prompted

2. Connect a TFTP server reachable at 192.168.11.10/24
   to the ethernet port. Serve the OpenWrt initramfs image as
   "openwrt.bin"

3. Boot the initramfs image using U-Boot
   ath> tftpboot 0x84000000 openwrt.bin
   ath> bootm 0x84000000

4. Copy the OpenWrt sysupgrade image to the device using scp and
   install it like a normal upgrade (with no need to keeping config
   since no config from "previous OpenWRT installation" could be kept
   at all)

   # sysupgrade -n /path/to/openwrt/sysupgrade.bin

Installation from Web Interface
------------

To flash just do a firmware upgrade from the stock firmware (Buffalo
branded dd-wrt) with squashfs-factory.bin

Signed-off-by: Edward Chow <equu@openmail.cc>
Link: https://github.com/openwrt/openwrt/pull/17227
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>