bmc: provide state change method

The state change method will allow pushing any state change logic that's
required into a convenient point where all state changes intersect.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: Id44a5180bc8d901ce19da69b9b0362dc9f5fb630
diff --git a/firmware_handler.hpp b/firmware_handler.hpp
index 0d86ef0..de37e20 100644
--- a/firmware_handler.hpp
+++ b/firmware_handler.hpp
@@ -167,6 +167,9 @@
         return state;
     };
 
+    /** Provide for any state change triggers in convenience handler. */
+    void changeState(UpdateState next);
+
   private:
     void addBlobId(const std::string& blob)
     {