Kernel: Include the new PIT class in system components

Author: https://github.com/supercomputer7
Commit: 895e874eb4
Pull-request: https://github.com/SerenityOS/serenity/pull/1274
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/shannonbooth

Kernel/Devices/PCSpeaker.cpp

@@ -25,8 +25,8 @@
  */
 
 #include <Kernel/Arch/i386/CPU.h>
-#include <Kernel/Arch/i386/PIT.h>
 #include <Kernel/Devices/PCSpeaker.h>
+#include <Kernel/Devices/PIT.h>
 #include <LibBareMetal/IO.h>
 
 void PCSpeaker::tone_on(int frequency)