Bluetooth: Add support for limited privacy mode

Introduce a limited privacy mode indicated by value 0x02 to the mgmt
Set Privacy command.

With value 0x02 the kernel will use privacy mode with a resolvable
private address. In case the controller is bondable and discoverable
the identity address will be used.

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