Bluetooth: Add support for sending New IRK event

This patch adds the necessary helper function to send the New IRK mgmt
event and makes sure that the function is called at when SMP key
distribution has completed. The event is sent before the New LTK event
so user space knows which remote device to associate with the keys.

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