Kernel: Rename HardwareTimer::change_function() => set_callback()

Also make it non-virtual since nothing needs to override it.

Kernel/Time/HardwareTimer.cpp

@@ -48,7 +48,7 @@ const char* HardwareTimer::purpose() const
     return model();
 }
 
-void HardwareTimer::change_function(Function<void(const RegisterState&)> callback)
+void HardwareTimer::set_callback(Function<void(const RegisterState&)> callback)
 {
     disable_irq();
     m_callback = move(callback);

Kernel/Time/HardwareTimer.h

@@ -48,7 +48,8 @@ public:
     virtual const char* model() const = 0;
     virtual const char* purpose() const override;
 
-    virtual void change_function(Function<void(const RegisterState&)>);
+    void set_callback(Function<void(const RegisterState&)>);
+
     virtual size_t ticks_per_second() const = 0;
 
     virtual bool is_periodic() const = 0;

Kernel/Time/TimeManagement.cpp

@@ -190,10 +190,10 @@ bool TimeManagement::probe_and_set_non_legacy_hardware_timers()
         }
     }
 
-    m_system_timer->change_function(Scheduler::timer_tick);
+    m_system_timer->set_callback(Scheduler::timer_tick);
     dbg() << "Reset timers";
     m_system_timer->try_to_set_frequency(m_system_timer->calculate_nearest_possible_frequency(1024));
-    m_time_keeper_timer->change_function(TimeManagement::update_time);
+    m_time_keeper_timer->set_callback(TimeManagement::update_time);
     m_time_keeper_timer->try_to_set_frequency(OPTIMAL_TICKS_PER_SECOND_RATE);
 
     return true;