[][kernel][mt7988][bsp][Rename MT7988C DTS to the MT7988D]

[Description]
Change DTS name of the MT7988C to the MT7988D.

[Release-log]
N/A


Change-Id: Ibf3b87684f224c235133472c8aa5e638b0afcf96
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7528542
9 files changed