Kernel+KeyboardSettings: Remove numlock syscall and implement ioctl

Author: https://github.com/EdwinHoksberg
Commit: 99328e1038
Pull-request: https://github.com/SerenityOS/serenity/pull/8474

Kernel/Devices/HID/KeyboardDevice.h

@@ -49,8 +49,6 @@ public:
             m_modifiers &= ~modifier;
     }
 
-    void set_num_lock(bool on) { m_num_lock_on = on; }
-
 protected:
     KeyboardDevice();
     mutable SpinLock<u8> m_queue_lock;