mvebu: add support for IIJ SA-W2

mvebu: add support for IIJ SA-W2

Internet Initiative Japan Inc. (IIJ) SA-W2 is a network appliance with
11ac (Wi-Fi 5) wlan, based on 88F6810.

Specification:

- SoC         : Marvell Armada 380 88F6810
- RAM         : DDR3 256 MiB (Micron MT41K64M16TW-107:J x2)
- Flash       : SPI-NOR 32 MiB (Winbond W25Q256JVFIQ)
- WLAN        : 2.4/5 GHz, Mini PCI-E
  - 2.4 GHz   : Silex SX-PCEGN (Atheros AR9287 (2T2R))
  - 5 GHz     : Silex SX-PCEAC (Qualcomm Atheros QCA9880 (3T3R))
- Ethernet    : 10/100/1000 Mbps x5
  - Switch    : Marvell 88E6172
- LEDs/Keys   : 12x/1x
- UART        : "CONSOLE" port (RJ-45, RS-232C)
  - settings  : 115200n8
  - assignment: 1:NC,  2:NC,  3:TXD, 4:GND,
                5:GND, 6:RXD, 7:NC,  8:NC
  - note      : compatible with Cisco console cable
- Power       : DC Input or PoE
  - DC Input  : 12 VDC, 3 A
  - PoE       : 802.3af
    - module  : Silvertel Ag9712-2BR
    - note    : USB ports shouldn't be used when powered by PoE
- Bootloader  : PMON2000 based
- Stock       : NetBSD based

Flash instruction using sysupgrade image:

1. Prepare TFTP server with IP address 192.168.0.10 and put sysupgrade
   image to TFTP directory
2. Connect PC to "GE0/PoE" port on SA-W2
3. Power on SA-W2, interrupt count-down by Esc and enter to bootloader
   CLI
4. Set IP address of the device

   address 192.168.0.1

5. Download sysupgrade image and flash to storage

   tftpload 192.168.0.10 <image name>
   firmwrite

   example:

   #tftpload 192.168.0.10 openwrt-mvebu-cortexa9-iij_sa-w2-squashfs-sysupgrade.bin
   Loading openwrt-mvebu-cortexa9-iij_sa-w2-squashfs-sysupgrade.bin
   loaded 8127268 byte(s)
   #firmwrite
   Erasing FLASH block  32 Done 0x00200000.
   Erasing FLASH block  33 Done 0x00210000.
   ...
   Erasing FLASH block 155 Done 0x009b0000.
   Erasing FLASH block 156 Done 0x009c0000.
   Programming FLASH. Done.
   Verifying FLASH. No Errors found.

6. Check the flashed firmware

   firmcheck

   example:

   #firmcheck
   [Normal firmware]
   ident: 'SEIL2015'
   copyright: 'ARM OpenWrt Linux-5.15.93'
   version format: 1
   version major: 9
   version minor: 99
   version release: 'r22060+36-5163bb5e54'
   body size: 3578524
   checksum: 0x8a083cb8

   [Rescue firmware]
   ident: 'SEIL2015'
   copyright: 'Copyright (c) 2017 Internet Initiative Japan Inc. All rights reserved.'
   version format: 1
   version major: 3
   version minor: 70
   version release: 'Release'
   body size: 10152458
   checksum: 0x8f9518c2

7. Boot with the flashed firmware

   boot

Note:

- The bootloader on this device is not U-Boot and it's environment space
  ("bootloader-env") has no compatibility with U-Boot tools.

- eth1 is connected to port6 of 88E6172 switch, but multi-cpu port can't
  be handled on Linux Kernel and not defined.

- Powering by PoE hasn't been tested yet.

- This device has 2x OS images on flash and they can be switched by
  setting "BOOTDEV" variable on bootloader CLI.
  That variable supports the following values:

  - "flash" : primary image on flash ("firmware")
  - "rescue": secondary image on flash ("rescue")
  - "usb"   : usb storage (broken?)
  - "lan0/1": network

  command to set:

  set BOOTDEV=<dev>

  example:

    set BOOTDEV=rescue

  This commit also supports booting from secondary partition.

- To execute initramfs image on bootloader CLI, use "go" command.
  ("go" command is not listed on the output of "help", but available)

  example (download and execute):

    address 192.168.0.1
    tftpload 192.168.0.10 openwrt-mvebu-cortexa9-iij_sa-w2-initramfs-kernel.bin
    go

MAC addresses:

LAN    : 00:E0:4D:xx:xx:19 (none)
WAN    : 00:E0:4D:xx:xx:18 (board_info, 0x6 (hex))
2.4 GHz: 84:25:3F:xx:xx:xx (Mini PCI-E card)
5 GHz  : 84:25:3F:xx:xx:xx (Mini PCI-E card)

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>