bluetooth: host: Fix stale RPA usage on advertiser restart

Regenerate RPA when re-enabling an advertising set if BT_ADV_RPA_VALID
flag was cleared while the advertiser was disabled.

When RPA rotation is triggered via le_force_rpa_timeout() while an
advertiser is disabled, the BT_ADV_RPA_VALID flag is cleared but the
RPA is not regenerated. Without this fix, re-enabling the advertiser
would use the stale RPA, violating Bluetooth privacy requirements.

Add !BT_ADV_RPA_VALID check to bt_le_ext_adv_start() for both
connectable and non-connectable advertisers to ensure fresh RPA
generation when needed.

This also ensures proper rpa_expired callback invocation for disabled
advertising sets per the bt_le_ext_adv_cb API contract.

Fixes regression introduced in #98117.

Signed-off-by: Pavel Vasilyev <[email protected]>

Author: PavelVPV

subsys/bluetooth/host/adv.c

@@ -1514,13 +1514,15 @@ int bt_le_ext_adv_start(struct bt_le_ext_adv *adv,
 		if (IS_ENABLED(CONFIG_BT_PRIVACY) &&
 		    !atomic_test_bit(adv->flags, BT_ADV_USE_IDENTITY) &&
 		    (!atomic_test_and_clear_bit(adv->flags, BT_ADV_RANDOM_ADDR_UPDATED) ||
-		     atomic_test_bit(adv->flags, BT_PER_ADV_ENABLED))) {
+		     atomic_test_bit(adv->flags, BT_PER_ADV_ENABLED) ||
+		     !atomic_test_bit(adv->flags, BT_ADV_RPA_VALID))) {
 			bt_id_set_adv_private_addr(adv);
 		}
 	} else {
 		if (!atomic_test_bit(adv->flags, BT_ADV_USE_IDENTITY) &&
 		    (!atomic_test_and_clear_bit(adv->flags, BT_ADV_RANDOM_ADDR_UPDATED) ||
-		     atomic_test_bit(adv->flags, BT_PER_ADV_ENABLED))) {
+		     atomic_test_bit(adv->flags, BT_PER_ADV_ENABLED) ||
+		     !atomic_test_bit(adv->flags, BT_ADV_RPA_VALID))) {
 			bt_id_set_adv_private_addr(adv);
 		}
 	}