LineageParts: Stats: Improve getting a valid carrier name

* Looking at our stats server, there are a lot of unknown carriers
* "Unknown" may be the result of the device not being registered to a
  network when the stats are collected, so in these cases we would simply
  go by whoever provided the SIM

Change-Id: I659c96d0d683109a75d9e12daa1d6fa457eb4840