Bluetooth: Add support for Not Connectable flag for Device Found events

The Device Found events of the management interface should indicate if
it is possible to connect to a remote device or if it is broadcaster
only advertising. To allow this differentation the Not Connectable flag
is introduced that will be set when it is known that a device can not
be connected.

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