[][Refactor mt7986 config-5.4 with mt7531 DSA support]

[Description]
Refactor mt7986 config-5.4 with mt7531 DSA support
1. enable DSA with mt7531 support
2. sync latest config-5.4

[Release-log]
N/A

Change-Id: Ib624cd9b0f22e5526c2b2594ce500e8a08226045
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4502410
1 file changed