Bluetooth: Fix link security setting when powering on

If a controller is powered on while the HCI_AUTO_OFF flag is set the
link security setting (HCI_LINK_SECURITY) might not be in sync with the
actual state of the controller (HCI_AUTH). This patch fixes the issue by
checking for inequality between the intended and actual settings and
sends a HCI_Write_Auth_Enable command if necessary.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>