mediatek: change Routerich AX3000 ubi size

mediatek: change Routerich AX3000 ubi size
All new routers are shipped with ubi size 112MB since early September.
Bootloader update required (ask vendor , see wiki)

These partitions weren't used:
firmware_backup
zrsave
config2

Signed-off-by: Romanov Danila <pervokur@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/16686
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
(cherry picked from commit d8a9669093359d60f4d6f183b58a22f24cf01731)
Link: https://github.com/openwrt/openwrt/pull/17097
Signed-off-by: Petr Štetiar <ynezz@true.cz>