With wrong rtwsta->mac_id, it can't send out ack properly when we receive
assoc response occasionally. Then, it failed to connect an AP.

The cause is that we store 'sta' and use it somewhere. To correct this,
remove the variable and use mac_id in drv_priv of 'sta' or 'vif' passed
by mac80211.
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20211201080607.11211-1-pkshih@realtek.com