Bluetooth: Provide remote OOB data for Secure Connections

When Secure Connections has been enabled it is possible to provide P-192
and/or P-256 data during the pairing process. The internal out-of-band
credentials storage has been extended to also hold P-256 data.

Initially the P-256 data will be empty and with Secure Connections enabled
no P-256 data will be provided. This is according to the specification
since it might be possible that the remote side did not provide either
of the out-of-band credentials.

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