Bluetooth: Don't use non-resolvable private address for passive scanning

The usage of non-resovlable private addresses for passive scanning is
a bad idea. Passive scanning will not send any SCAN_REQ and thus using
your identity address for passive scanning is not a privacy issue.

It is important to use the identity address during passive scanning
since that is the only way devices using direct advertising will be
reported correctly by the controller. This is overlooked detail in
the Bluetooth specification that current controllers are not able
to report direct advertising events for other than their current
address.

When remote peers are using direct advertising and scanning is done
with non-resolvable private address these devices will not be found.

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