TMF: Return null for unimplemented getValidTraceTypes

The implementation of the getValidTraceTypes will be implemented at the same time for all the IAnalysisModuleHelper and when each analysis will provide their requirements.

Change-Id: I764291e0ca5281550a16d61a9aa8dbf5ca05d390
Signed-off-by: Mathieu Rail <contact@mathieurail.com>
Signed-off-by: Guilliano Molaire <guilliamo-jaime.molaire@polymtl.ca>