Bluetooth: Track number of added devices with HCI_AUTO_CONN_REPORT

To be able to make the right choice of whether to start passive scanning
or to send out a mgmt_device_found event we need to know if there are
any devices in the le_conn_params list with the auto_connect value set
to HCI_AUTO_CONN_REPORT. This patch adds a counter for this kind of
devices.

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