Bluetooth: Check for P-256 OOB values in Secure Connections Only mode

If Secure Connections Only mode has been enabled, the it is important
to check that OOB data for P-256 values is provided. In case it is not,
then tell the remote side that no OOB data is present.

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