Bluetooth: Disable HCI_CONNECTABLE based passive scanning for now

When HCI_CONNECTABLE is set the code has been enabling passive scanning
in order to be consistent with BR/EDR and accept connections from any
device doing directed advertising to us. However, some hardware
(particularly CSR) can get very noisy even when doing duplicates
filtering, making this feature waste resources.

Considering that the feature is for fairly corner-case use (devices
who'd use directed advertising would likely be in the whitelist anyway)
it's better to disable it for now. It may still be brought back later,
possibly with a better implementation (e.g. through improved scan
parameters).

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