NethVoice: add support for NethPhone v64

[andrea-marchionni]

Description

Add support for the new NethPhone v64 model in NethVoice phone provisioning.

Steps to reproduce

1. Open NethVoice phone configuration.
2. Add or configure a phone.
3. Select the NethPhone model.

Expected behavior

NethPhone v64 is available as a supported and configurable phone model.

Actual behavior

NethPhone v64 is not available among the configurable phone models.