[][kernel][mt7988][dts][Refactor UBI partition size]

[Description]
Refactor UBI partition size to 128M

[Release-log]

Change-Id: I7a13a2ab1618866a8fc6eb0ad4d239781faf390f
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6816130
6 files changed