Bluetooth: Convert inquiry cache to use standard list types

This makes it possible to use the convenience functions provided for
standard kernel list types and it also makes it easier to extend the use
of the cache for the management interface where e.g. name resolving
control will be needed.

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