prov_write_ccc() function

For provisioner acting as a GATT client, it may follow the procedures listed below. 1. Create connection with the unprovisioned device 2. Exchange MTU size 3. Find Mesh Prov Service in the device's service database 4. Find Mesh Prov Data In/Out characteristic within the service 5. Get CCC of Mesh Prov Data Out Characteristic 6. Set the Notification bit of CCC