Bluetooth: Add dev_flags to struct hci_dev

This patch adds the dev_flags field to struct hci_dev. This new
flags variable should be used to define flags related to BR/EDR
and/or LE controller itself. It should be used to define flags
which represents states from the controller. The dev_flags is
cleared in case the controller sends a Reset Command Complete
Event to the host.

Also, this patch adds the HCI_LE_SCAN flag which was created to
track if the controller is performing LE scan or not. The flag
is set/cleared when the controller starts/stops scanning.

This is an initial effort to stop using hdev->flags to define
internal flags since it is exported to userspace by an ioctl.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>