Bluetooth: Fix verifying confirm value when lacking remote OOB data

If we haven't received remote OOB data we cannot perform any special
checks on the confirm value. This patch updates the check after having
received the public key to only perform the verification if we have
remote OOB data present.

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