Bluetooth: Fix using advertising instance duration as timeout

When using LE Set Extended Advertising Enable command the duration
refers to the lifetime of instance not the length which is actually
controlled by the interval_min and interval_max when setting the
parameters.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>