wifi: rtl8xxxu: support multiple interfaces in configure_filter()

As we only want to support AP mode/sending beacons on port 0, change
from priv->vif to priv->vifs[0] in the check for AP mode.
Additionally, if we are in AP mode, don't filter RX beacon and probe
response frames to still allow working STATION mode on the other
interface.

Signed-off-by: Martin Kaistra <martin.kaistra@linutronix.de>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20231222101442.626837-13-martin.kaistra@linutronix.de