Bluetooth: Use Identity Address in Device Found event

Whenever a device uses an RPA we want to have user space identify it by
its Identity Address if we've got an IRK available for it. This patch
updates the Device Found mgmt event to contain the Identity Address if
an IRK is available for the device in question.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>