Bluetooth: Add support for Add/Remove Device management commands

This allows adding or removing devices from the background scanning
list the kernel maintains. Device flagged for auto-connection will
be automatically connected if they are found.

The passive scanning required for auto-connection will be started
and stopped on demand.

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