[] [MT7981: add rootwait attributes]

[Description]
Add rootwait attributes

[Release-log]
N/A

[Test]
Build pass and platform bootup

Change-Id: I5d2589880c7b4aea253154d8e3cc5561b204f659
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7249039
4 files changed