This permission isn't needed right now, since there aren't actually any
public APIs that require it. (There are a few calls in the ITelephony
interface that do, but they're all hidden.)
Since there's no good reason for 3rd party apps to declare it, let's
mark it signatureOrSystem for now. We can bring it back -- and probably
split it apart into multiple finer-grained permissions -- once we
finally expose full telephony APIs to 3rd party apps (see bug 1043005).
Bug: 2989096
Change-Id: Idf898d5e12d648a959f622cd815e75597195aa82
f4ece2086f