mediatek: extract DTS include for zbt z8103ax

mediatek: extract DTS include for zbt z8103ax

- Use .dtsi for old z8103ax featuring a 64M Nand
- Prepare .dtsi for model C of z8103ax featuring a 128M Nand

This .dtsi is supposed to match boards labeled as hardware
revision Z8103AX_V01. Model variant D of zbt-z8103ax appears
to use very same board.

DTS include does also

- set wifi mac addresses in &wifi section
- set eth mac addresses in &eth section
- set LAN switch mac addresses in &switch section

All of the above allows to get rid of 11_fix_wifi_mac script

Signed-off-by: Jörg Seitz <github.joeterminal@xoxy.net>
Link: https://github.com/openwrt/openwrt/pull/19823
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>