Bluetooth: Move SMP LTK notification after key distribution

This patch moves the SMP Long Term Key notification over mgmt from the
hci_add_ltk function to smp.c when both sides have completed their key
distribution. This way we are also able to update the identity address
into the mgmt_new_ltk event.

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