[][OpenWrt Dev][Add support for mmc dual-boot to reserve rootfs_data]

[Description]
Add support for mmc dual-boot to reserve rootfs_data

[Release-log]
N/A

Change-Id: Icec46b6ce94b85c72baabf5523919476cc452ba7
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6105791
1 file changed