Bluetooth: Use hci_copy_identity_addr() helper for SMP chan creation

The only reason the SMP code is essentially duplicating the
hci_copy_identity_addr() function is that the helper returns the address
type in the HCI format rather than the three-value format expected by
l2cap_chan. This patch converts the SMP code to use the helper and then
do a simple conversion from one address type to another.

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