kirkwood: add support for Iomega Storcenter ix2-200

kirkwood: add support for Iomega Storcenter ix2-200

Iomega Storcenter ix2-200 is a dual SATA NAS powered by a Marvell
 Kirkwood SoC clocked at 1GHz. It has 256MB of RAM and 32MB of
 flash memory, 3x USB 2.0 and 1x 1Gbit/s NIC

Specification:
- SoC: Marvell Kirkwood 88F6281
- CPU/Speed: 1000Mhz
- Flash-Chip: Hynix NAND
- Flash size: 32 MiB,erase size:16 KiB,page size:512,OOB size:16
- RAM: 256MB
- LAN: 1x 1000 Mbps Ethernet
- WiFi: none
- 3x USB 2.0
- UART: for serial console

Installation instructions - easy steps:
1. download factory.bin and copy into tftp server
2. access uboot environment with serial cable and run
    ```
    setenv mainlineLinux yes
    setenv arcNumber 1682
    setenv console 'console=ttyS0,115200n8'
    setenv mtdparts 'mtdparts=orion_nand:0x100000@0x000000(u-boot)ro,0x20000@0xA0000(u-boot environment)ro,0x300000@0x100000(kernel),0x1C00000@0x400000(ubi)'
    setenv bootargs_root 'root='
    setenv bootcmd 'setenv bootargs ${console} ${mtdparts} ${bootargs_root}; nand read.e 0x800000 0x100000 0x300000; bootm 0x00800000'
    saveenv
    setenv serverip 192.168.1.1
    setenv ipaddr 192.168.1.13
    tftpboot 0x00800000 factory.bin
    nand erase 0x100000 $(filesize)
    nand write 0x00800000 0x100000 $(filesize)
    run bootcmd
    ```
3. access openwrt by dhcp ip address assigned by your router (p.ex: 192.168.1.13)

Installation steps nand bad blocks proof:
1. download initramfs-uImage and copy into usb ext2 partition
    ```
    mkfs.ext2 -L ext2 /dev/sdh1
    mount -t ext2 /dev/sdh1 /mnt
    cp initramfs-uImage /mnt/initramfs.bin
    umount /mnt
    ```
2. access uboot environment with serial cable and run
    ```
    setenv mainlineLinux yes
    setenv arcNumber 1682
    setenv console 'console=ttyS0,115200n8'
    setenv mtdparts 'mtdparts=orion_nand:0x100000@0x000000(u-boot)ro,0x20000@0xA0000(u-boot environment)ro,0x300000@0x100000(kernel),0x1C00000@0x400000(ubi)'
    setenv bootargs_root 'root='
    setenv bootcmd 'setenv bootargs ${console} ${mtdparts} ${bootargs_root}; nand read.e 0x800000 0x100000 0x300000; bootm 0x00800000'
    saveenv
    usb reset; ext2load usb 0:1 0x00800000 /initramfs.bin; bootm 0x00800000
    ```
3. log into openwrt and sysupgrade to install into flash
    ```
    sysupgrade -n /tmp/sysupgrade.bin
    ```
4. access openwrt by dhcp ip address assigned by your router (p.ex: 192.168.1.13)

Signed-off-by: Ademar Arvati Filho <arvati@hotmail.com>
(backported from 27b2f0fc0fc5513304a5be3c5b8cb23aeb09e6f5)