wifi: mac80211: make 4addr null frames using min_rate for WDS

WDS needs 4addr packets to trigger AP for wlan0.sta creation.
However, the 4addr null frame is sent at a high rate so that
sometimes the AP can't receive it. Switch to using min rate.

Signed-off-by: Lian Chen <lian.chen@mediatek.com>
Link: https://lore.kernel.org/r/20220714091636.59107-1-lian.chen@mediatek.com


Signed-off-by: Johannes Berg <johannes.berg@intel.com>