[][MAC80211][infra][Update dts for mt76 to support flash mode]

[Description]
Add slot0 in dts for mt76 to support flash mode

[Release-log]
N/A

Change-Id: I3ee413070f2a93090355dcdae1f7e742cbab321f
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7077950
3 files changed