wifi: rtl8xxxu: support multiple interfaces in bss_info_changed()

Call set_linktype and set_bssid now with correct port_num. Call
stop_tx_beacon only for port 0, as we don't support beacons on port 1.
Explicit changes to BEACON will only happen for AP type interfaces, so
we don't need an additional check there.

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/20231222101442.626837-16-martin.kaistra@linutronix.de