[][OpenWrt Dev][Add mmc support to mt7986]

[Description]
Add mmc support to mt7986

[Release-log]
N/A

Change-Id: Ief15334be21b012bd6346550ba7d3e14174fdaa1
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4586299
1 file changed