Add missing const keyword

ftrace.cpp

@@ -33,7 +33,7 @@ FTraceLogger::FTraceLogger(QObject *parent)
     }
 }
 
-bool FTraceLogger::isEnabled()
+bool FTraceLogger::isEnabled() const
 {
     return m_file.isOpen();
 }

ftrace.h

@@ -37,7 +37,7 @@ public:
     /**
      * Enabled through DBus and logging has started
      */
-    bool isEnabled();
+    bool isEnabled() const;
 
     /**
      * Main log function