sim: Remove test for non-NULL this in Event

The method Event::initialized() tests if this != NULL as a part of the
expression that tests if an event is initialized. The only case when
this check could be false is if the method is called on a null
pointer, which is illegal and leads to undefined behavior (such as
eating your pets) according to the C++ standard. Because of this,
modern compilers (specifically, recent versions of clang) warn about
this which we treat as an error. This changeset removes the redundant
check to fix said warning.

src/sim/eventq.hh

@@ -239,7 +239,7 @@ class Event : public EventBase, public Serializable
     bool
     initialized() const
     {
-        return this && (flags & InitMask) == Initialized;
+        return (flags & InitMask) == Initialized;
     }
 
   protected: