[][OpenWrt Dev][Enable new NMBM feature for mt7986]

[Description]
Add NMBM usability checking option on erased block for mt7986 dts

[Release-log]
N/A

Change-Id: Ic1ee2730b20ae36545ad84fd53a97a79b76c22fe
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4649346
2 files changed