[][kernel][mt7988][bsp][Add MT7988C DTS]

[Description]
Add MT7988C DTS.

[Release-log]
N/A


Change-Id: I5caf829296387d65eeee7038619471df14f04add
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6998165
10 files changed