Bluetooth: Clear P-192 values for OOB when in Secure Connections Only mode

When Secure Connections Only mode has been enabled and remote OOB data
is requested, then only provide P-256 hash and randomizer vaulues. The
fields for P-192 hash and randomizer should be set to zero.

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