Bluetooth: Use cmd_complete callback for authentication mgmt commands

This patch converts the user confirmation & PIN code mgmt commands to
take advantage of the new cmd_complete callback for pending mgmt
commands. The patch also adds a new generic addr_cmd_complete() helper
function to be used with commands that send a mgmt_addr_info response
based on a mgmt_addr_info in the beginning of the command parameters.

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