[][mac80211][wifi6][mt76][fix debugfs for pleinfo and token_txd]

[Description]
Fix debugfs for pleinfo and token_txd
Assign vif to mt7915_vif.mt7915_sta.vif because pleinfo dump would also need to
include token used by AP broadcast.

[Release-log]
N/A

Change-Id: I657e63a8f49db513a9564b31cdf7bcce7622d90b
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7901953
2 files changed