sim: Remove the unused SimObject::regFormulas method

Simulation objects normally register derived statistics, presumably
what regFormulas originally was meant for, in regStats(). This patch
removes regRegformulas since there is no need to have a separate
method call to register formulas.

src/sim/sim_object.cc

@@ -104,11 +104,6 @@ SimObject::regStats()
 {
 }
 
-void
-SimObject::regFormulas()
-{
-}
-
 void
 SimObject::resetStats()
 {

src/sim/sim_object.hh

@@ -126,7 +126,6 @@ class SimObject : public EventManager, public Serializable
 
     // register statistics for this object
     virtual void regStats();
-    virtual void regFormulas();
     virtual void resetStats();
 
     /**