mpc85xx: add support for Hewlett Packard MSM460

mpc85xx: add support for Hewlett Packard MSM460

Hardware
--------
CPU:  Freescale P1020 2xe500 PPC
RAM:  256M DDR3 (Micron MT41J64M16JT-15E:G "D9MNJ")
NAND: 128M (Micron 2CA1)
BTN:  1x Reset
LED:  Power - ETH - Radio1 - Radio2
UART: RJ-45 Cisco Pinout - 115200 8N1

Installation
------------
NOTE: You can find a repo with up-to-date instructions as well as
the required files here:

https://github.com/blocktrron/msm460-flashing

Required files
==============
You need a command-files as well as a U-Boot image.

The command-file has the following content (padded to 131072 bytes).

If you copy paste these, remove the newlines!

```
U-BOOT setenv ethaddr 02:03:04:05:06:07; setenv ipaddr 192.168.1.1;
setenv serverip 192.168.1.66; tftpboot 0x3000000 msm460-uboot.bin;
nand device; nand erase 0 0xC0000; nand write 0x3000000 0x0 0xC0000; reset
```

You can download the required U-Boot from this repository:

https://github.com/blocktrron/u-boot-msm/releases

Preparation
===========
Prepare a TFTP server serving two files:

 - U-Boot NAND image as `msm460-uboot.bin`.
 - OpenWrt factory image as `msm460-factory.bin`
 - Command-file names `commands.tftp`

You can start a TFTP server in the current directory using dnsmasq:

```bash
sudo dnsmasq --no-daemon --listen-address=0.0.0.0 \
    --port=0 --enable-tftp=enxd0 --tftp-root="$(pwd)" \
    --user=root --group=root
```
Replace `enxd0` with the name of your network interface.

Procedure
=========
1. Assign yourself the IP-Address 192.168.1.66/24.
3. Connect the Router to the PC while keeping the reset button
   pressed.
4. The LEDs will eventually begin to flash.
   They will start to flash faster after around 15 seconds.
5. Release the reset button.
6. Start a new shell
7. Make sure you are currently in the directory where the tftp server
   is located.
8. Run the following command:

```bash
tftp 192.168.1.1 -m binary -c put commands.tftp nflashd.cccc9999
```

You get the message "Transfer timed out."
To find out if you have been successful, please check the
blinking LED Pattern.

Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit af329ec38980e2f706411a11b9f344a62eb0dd8f)
Signed-off-by: David Bauer <mail@david-bauer.net>