Kernel: Reorganize Arch/x86 directory to Arch/x86_64 after i686 removal

No functional change.

Kernel/Arch/x86_64/Delay.cpp

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Arch/Delay.h>
+#include <Kernel/Arch/x86_64/IO.h>
+
+namespace Kernel {
+
+void microseconds_delay(u32 microseconds)
+{
+    IO::delay(microseconds);
+}
+
+}