mediatek: Add support for D-Link EAGLE PRO AI M32

mediatek: Add support for D-Link EAGLE PRO AI M32

Specification:
 - MT7622BV SoC with 2.4GHz wifi
 - MT7975AN + MT7915AN for 5GHz
 - MT7531BE Switch
 - 512MB RAM
 - 128 MB flash
 - 3 LEDs (red, orange, white)
 - 2 buttons (WPS and Reset)

MAC addresses:
 - WAN MAC is stored in partition "Odm" at offset 0x83
 - LAN (as printed on the device) is WAN MAC + 1
 - WLAN MAC (2.4 GHz) is WAN MAC + 2
 - WLAN MAC (5GHz) is WAN MAC + 3

Disassembly: Remove 4 screws in the bottom and 2 screws in the top (after removing the blue cover on the top), then the board can be pulled out.

The pins for the serial console are already labeled on the board (VCC, TX, RX, GND). Serial settings: 3.3V, 115200,8n1

Flashing via Recovery Web Interface:
- Set your IP address to 192.168.0.10, subnetmask 255.255.255.25
- Press the reset button while powering on the deivce
- Keep the reset button pressed until the status LED blinks fast
- Open a Chromium based and goto http://192.168.0.1
- Download openwrt-mediatek-mt7622-dlink_eagle-pro-ai-m32-a1-squashfs-recovery.bin

Flashing via uBoot:
- Open the case, connect to the UART console
- Set your IP address to 10.10.10.3, subnet mask 255.255.255.0. Connect to one of the LAN interfaces of the router
- Run a tftp server which provides openwrt-mediatek-mt7622-dlink_eagle-pro-ai-m32-initramfs-kernel.bin. You can rename the file to iverson_uImage (no extension), then you don't have to enter the whole file name in uboot later.
- Power on the device and select "1. System Load Linux to SDRAM via TFTP." in the boot menu
- Enter image file, tftp server IP and device IP (if they differ from the default).
- TFTP download to RAM will start. After a few seconds OpenWrt initramfs should start
- The initramfs is accessible via 192.168.1.1, change your IP address accordingly (or use multiple IP addresses on your interface)
- Create a backup of the Kernel1 partition, this file is required if a revert to stock should be done later
- Perform a sysupgrade using openwrt-mediatek-mt7622-dlink_eagle-pro-ai-m32-squashfs-sysupgrade.bin
- Reboot the device. OpenWrt should start from flash now

Revert back to stock using the Recovery Web Interface:
- Set your IP address to 192.168.0.10, subnetmask 255.255.255.25
- Press the reset button while powering on the deivce
- Keep the reset button pressed until the status LED blinks fast
- Open a Chromium based and goto http://192.168.0.1
- Flash a decrypted firmware image from D-Link. Decrypting an firmware image is described below.

Decrypting a D-Link firmware image:
- Download https://github.com/RolandoMagico/firmware-utils/blob/M32/src/m32-firmware-util.c
- Compile a binary from the downloaded file, e.g. gcc m32-firmware-util.c -lcrypto -o m32-firmware-util
- Run ./m32-firmware-util M32 --DecryptFactoryImage <OriginalFirmware> <OutputFile>
- Example for firmware 1.03.01_HOTFIX: ./m32-firmware-util M32 --DecryptFactoryImage M32-REVA_1.03.01_HOTFIX.enc.bin M32-REVA_1.03.01_HOTFIX.decrypted.bin

Revert back to stock using uBoot:
- Open the case, connect to the UART console
- Set your IP address to 10.10.10.3, subnet mask 255.255.255.0. Connect to one of the LAN interfaces of the router
- Run a tftp server which provides the previously created backup of the Kernel1 partition. You can rename the file to iverson_uImage (no extension), then you don't have to enter the whole file name in uboot later.
- Power on the device and select "2. System Load Linux Kernel then write to Flash via TFTP." in the boot menu
- Enter image file, tftp server IP and device IP (if they differ from the default).
- TFTP download to FLASH will start. After a few seconds the stock firmware should start again

There is also an image openwrt-mediatek-mt7622-dlink_eagle-pro-ai-m32-a1-squashfs-tftp.bin which can directly be flashed via U-Boot and TFTP. It can be used if no backup of the Kernel1 partition is reuqired.

Flahsing via OEM web interface is currently not possible, the OEM images are encrypted and require a specific memory layout which is not compatible to the partition layout of OpenWrt.

Signed-off-by: Roland Reinl <reinlroland+github@gmail.com>