Expand VTY option which controls use of TCH for signalling

For statistical clarity and site tuning, it is sometimes
desirable to completely disable the use of TCH for signaling.

In the existing version of this VTY command, there is no way to
accomplish this. We can only restrict TCH for signaling non-voice
related actions.

This patch deprecates 'allow-tch-for-signalling (0|1)' and
adds 'tch-signalling-policy (never|emergency|voice|always)' to
provide more options.

Change-Id: I4459941ddad4e4a3bec8409b180d9a23a735e640
5 files changed