ipq806x: add support for Nokia Airscale AC400i

ipq806x: add support for Nokia Airscale AC400i

Hardware
--------

SoC:    Qualcomm IPQ8065
RAM:    512 MB DDR3
Flash:  256 MB NAND (Macronix MX30UF2G18AC) (split into 2x128MB)
        4 MB SPI-NOR (Macronix MX25U3235F)
WLAN:   Qualcomm Atheros QCA9984 - 2.4Ghz
        Qualcomm Atheros QCA9984 - 5Ghz
ETH:    eth0 - POE (100Mbps in U-Boot, 1000Mbps in OpenWrt)
        eth1 - (1000Mbps in both)
        Auto-negotiation broken on both.
USB:    USB 2.0
LED:    5G, 2.4G, ETH1, ETH2, CTRL, PWR (All support green and red)
BTN:    Reset
Other:  SD card slot (non-functional)
Serial: 115200bps, near the Ethernet transformers, labeled 9X.
        Connections from the arrow to the 9X text:
		[NC] - [TXD] - [GND] - [RXD] - [NC]

Installation
------------

0. Connect to the device
Plug your computer into LAN2 (1000Mbps connection required).
If you use the LAN1/POE port, set your computer to force a 100Mbps link.

Connect to the device via TTL (Serial) 115200n8.
Locate the header (or solder pads) labeled 9X,
near the Ethernet jacks/transformers.
There should be an arrow on the other side of the header marking.
The connections should go like this:
(from the arrow to the 9X text): NC - TXD - GND - RXD - NC

1. Prepare for installation
While the AP is powering up, interrupt the startup process.
MAKE SURE TO CHECK YOUR CURRENT PARTITION!

If you see: "Current Partition is : partB" or
"Need to switch partition from partA to partB",
you have to force the device into partA mode, before continuing.
This can be done by changing the PKRstCnt to 5 and resetting the device.

setenv PKRstCnt 5
saveenv
reset

After you interrupt the startup process again,
you should see: Need to switch partition from partB to partA

You can now continue to the next step.

If you see: "Current Partition is : partA",
you can continue to the next step.

2. Prevent partition switching.
To prevent the device from switching partitions,
we are going to modify the startup command.
set bootcmd "setenv PKRstCnt 0; saveenv; bootipq"
setenv

3. First boot
Now, we have to boot the OpenWrt intifs.
The easiest way to do this is by using Tiny PXE.
You can also use the normal U-Boot tftp method.

Run "bootp" this will get an IP from the DHCP server
and possibly the firmware image.
If it doesn't download the firmware image, run "tftpboot".

Now run "bootm" to run the image.

You might see:
"ERROR: new format image overwritten - must RESET the board to recover"
this means that the image you are trying to load is too big.
Use a smaller image for the initial boot.

4. Install OpenWrt from initfs
Once you are booted into OpenWrt,
transfer the OpenWrt upgrade image and
use sysupgrade to install OpenWrt to the device.

Signed-off-by: Kristjan Krušič <kristjan.krusic@krusic22.com>
[ drop -2G and -5G from variant BDF ]
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>