lantiq: add support for Arcadyan VRV9510KWAC23

lantiq: add support for Arcadyan VRV9510KWAC23

The Arcadyan VRV9510KWAC23 (trade name Livebox Next) is a Lantiq router distributed by some spanish ISPs

Hardware:
-   SoC: Lantiq VRX200
-   CPU: 2x MIPS 34Kc 500 MHz
-   RAM: 256 MiB DDR2
-   Flash: 128 MiB NAND
-   Ethernet: Built-in Gigabit Ethernet switch, 5x 1GbE
-   Wifi 2.4GHz: Broadcom BCM43222KFBG 802.11b/g/b MIMO 2T2R
-   Wifi 5GHz: Broadcom BCM4360KMLG 802.11ac MIMO 3T3R
-   USB: 2x USB 2.0
-   DSL: Built-in VDSL/ADSL2+ XWAY VRX208
-   LEDs: 8x
-   Buttons: 4x
-   Phone: Lantiq PEF 42068 V XWAY SLIC120

Install instructions:
Detailed instructions can be found on the wiki https://openwrt.org/toh/arcadyan/vrv9510kwac23
1. Boot into UART mode and upload the the https://raw.githubusercontent.com/danielhuici/arcadyan-vrv9510kwac23-utils/main/u-boot.asc file via serial console to boot into U-Boot.
2. Perform a backup of the NAND
3. Setup a TFTP server and serve the https://github.com/danielhuici/arcadyan-vrv9510kwac23-utils/raw/main/u-boot.ltq.lzo.nandspl. Replace the OEM bootloader with this one. Erase your NAND and write the image into it
4. Reboot the router
5. Serve the OpenWrt ramdisk image on your TFTP server and boot it via U-Boot
6. When OpenWrt boots, flash the SquashFS OpenWrt image using LuCi interface, so OpenWrt gets installed into the NAND

Signed-off-by: Daniel Huici <danielhuici@hotmail.com>