ramips: fix LAN/WAN MAC addresses of Xiaomi MiWiFi Mini board

ramips: fix LAN/WAN MAC addresses of Xiaomi MiWiFi Mini board

Based on stock firmware tests, both LAN and WAN ports use the
MAC address from 0x28 on factory partition.

In OpenWrt, this one is already set in DTS. This patch removes the
local bit set in 02_network previously, and adjusts LAN/WAN
addresses as on stock firmware.

Note that in tests we found a MAC address in 0x2e that is the one
in 0x28 plus 1. Since stock firmware does not use it though, we
do not use it either.

Thanks to Chih-Wei Chen for testing this on his device.

ref: https://github.com/openwrt/openwrt/pull/2497

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>