RIL: set responseCellInfoList protected to override in sub classes

Change-Id: Ibbbee0c1a59ab2be6b71fc2f70c6279314b55d6e
Proper supplementary service notification handling (2/5).

Allow registering SSN listeners, and add missing constants.

Change-Id: I339a395fda5cca7617e7619cfc93312a1282f60e