Kernel: Don't directly include <Kernel/Arch/x86/TrapFrame.h>

This adds a new arch-independent header which in turn includes the
correct header for the build architecture.

Kernel/Scheduler.cpp

@@ -9,7 +9,7 @@
 #include <AK/Singleton.h>
 #include <AK/Time.h>
 #include <Kernel/Arch/InterruptDisabler.h>
-#include <Kernel/Arch/x86/TrapFrame.h>
+#include <Kernel/Arch/TrapFrame.h>
 #include <Kernel/Debug.h>
 #include <Kernel/Panic.h>
 #include <Kernel/PerformanceManager.h>