Bluetooth: controller: Fix HCI Reset hang

Issuing HCI reset command while having connections sometimes
hung the controller.

ll_reset supplied invalid stop ticker id to role_disable
when trying to stop all connections. Connection role does
not utilize stop ticker. The invalid ticker id supplied
referenced memory outside the pool of tickers and based on
what the content is in RAM there, the controller would hang
trying to stop connections.

Fixed by not calling the ticker_stop interface with invalid
ticker ids.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>