Bluetooth: Introduce hdev->pending_auto_conn list

This patch introduces the hdev->pending_auto_conn list which holds
the device addresses the kernel should autonomously connect. It also
introduces some helper functions to manipulate the list.

The list and helper functions will be used by the next patch which
implements the LE auto connection infrastructure.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Introduce LE auto connection infrastructure

This patch introduces the LE auto connection infrasctructure.
This infrastructre will be used to implement the auto_connect
options from hci_conn_params.

The auto connection mechanism works as follows: When the first
device address is inserted into hdev->pending_auto_con list, we
start the background scanning. Once the target device is found
in range, the kernel creates the connection. If connection is
established successfully, the device address is removed from
hdev->pending_auto_conn list. Finally, when the last device
address is removed, the background scanning is stopped.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>