nl80211: Set all BSS interfaces down when tearing down AP in MBSS mode

If the interface was not added by hostapd, it could have been left up
when disabling the AP.

Signed-off-by: Maxime Bizon <mbizon@freebox.fr>

src/drivers/driver_nl80211.c

@@ -10018,6 +10018,8 @@ static int wpa_driver_nl80211_if_remove(struct i802_bss *bss,
 				/* Unsubscribe management frames */
 				nl80211_teardown_ap(bss);
 				nl80211_destroy_bss(bss);
+				if (!bss->added_if)
+					i802_set_iface_flags(bss, 0);
 				os_free(bss);
 				bss = NULL;
 				break;