ipq806x: add support for Arris TR4400 v2 / RAC2V1A

ipq806x: add support for Arris TR4400 v2 / RAC2V1A

Hardware specs:
  SoC: Qualcomm IPQ8065 (dual core Cortex-A15)
  RAM: 512 MB DDR3
  Flash: 256 MB NAND, 32 MB NOR
  WiFi: QCA9983 2.4 GHz, QCA9984 5 GHz
  Switch: QCA8337
  Ethernet: 5x 10/100/1000 Mbit/s
  USB: 1x USB 3.0 Type-A
  Buttons: WPS, Reset
  Power: 12 VDC, 2.5 A

Ethernet ports:
  1x WAN: connected to eth2
  4x LAN: connected via the switch to eth0 and eth1
          (eth0 is disabled in OEM firmware)

MAC addresses (OEM and OpenWrt):
  fw_env @ 0x00  d4:ab:82:??:??:?a  LAN (eth1)
  fw_env @ 0x06  d4:ab:82:??:??:?b  WAN (eth2)
  fw_env @ 0x0c  d4:ab:82:??:??:?c  WLAN 2.4 GHz (ath1)
  fw_env @ 0x12  d4:ab:82:??:??:?d  WLAN 5 GHz (ath0)
  fw_env @ 0x18  d4:ab:82:??:??:?e  OEM usage unknown (eth0 in OpenWrt)

  OID d4:ab:82 is registered to:
  ARRIS Group, Inc., 6450 Sequence Drive, San Diego CA 92121, US

More info:
  https://openwrt.org/inbox/toh/arris/tr4400_v2

IMPORTANT:

This port requires moving the 'fw_env' partition prior to first boot to
consolidate 70% of the usable space in flash into a contiguous partition.
'fw_env' contains factory-programmed MAC addresses, SSIDs, and passwords.
Its contents must be copied to 'rootfs_1' prior to booting via initramfs.
Note that the stock 'fw_env' partition  will be wiped during sysupgrade.

A writable 'stock_fw_env' partition pointing to the old, stock location
is included in the port to help rolling back this change if desired.

Installation:

- Requires serial access and a TFTP server.
- Fully boot stock, press ENTER, type in:
mtd erase /dev/mtd21
dd if=/dev/mtd22 bs=128K count=1 | mtd write - /dev/mtd21
umount /config && ubidetach -m 23 && mtd erase /dev/mtd23
- Reboot and interrupt U-Boot by pressing a key, type in:
set mtdids 'nand0=nand0'
set mtdparts 'mtdparts=nand0:155M@0x6500000(mtd_ubi)'
set bootcmd 'ubi part mtd_ubi && ubi read 0x44000000 kernel && bootm'
env save
- Setup TFTP server serving initramfs image as 'recovery.bin', type in:
set ipaddr 192.168.1.1
set serverip 192.168.1.2
tftpboot recovery.bin && bootm
- Use sysupgrade to install squashfs image.

This port is based on work done by AmadeusGhost <amadeus@jmu.edu.cn>.

Signed-off-by: Rodrigo Balerdi <lanchon@gmail.com>
[add 5.15 changes for 0069-arm-boot-add-dts-files.patch]
Signed-off-by: Sungbo Eo <mans0n@gorani.run>