Bluetooth: controller: Fix reset with ext adv enabled

We need to make sure aux is cleared on reset, otherwise we may end up
with legacy advertising with aux.

Signed-off-by: Andrzej Kaczmarek <andrzej.kaczmarek@codecoup.pl>

subsys/bluetooth/controller/ll_sw/ull_adv.c

@@ -1419,6 +1419,7 @@ int ull_adv_reset_finalize(void)
 
 #if defined(CONFIG_BT_CTLR_ADV_EXT)
 		adv->is_created = 0;
+		lll->aux = NULL;
 #endif
 		lll_adv_data_reset(&lll->adv_data);
 		lll_adv_data_reset(&lll->scan_rsp);