Implement GMM State using osmocom FSM

State machine inspired in the one from TS 24.008 4.1.3.3.1. Some state
transitions are inroduced in the code but are still commented out since
we lack some functionalitites or improvements in the code to handle
different scenarios.

Most of the logic is still outside of the FSM, but at least now the
states are handled in a sane way triggered by events.

Change-Id: Idecb43c10d66224d4f9ba9320825040ce6cf9a07
2 files changed