kernel: add some basic features

+ feat list:
+ * gdt/idt
+ * brokie pmm

kernel/src/arch/x86_64/cpu.c

@@ -1,7 +1,21 @@
+/*
+ *  The Soaplin Kernel
+ *  Copyright (C) 2025 The SILD Project
+ *
+ *  cpu.c - x86_64 CPU control implementation.
+ */
+
 #if defined (__x86_64__)
 
+#include <arch/x86_64/gdt.h>
+#include <arch/x86_64/idt.h>
 #include <arch/cpu.h>
 
+void arch_init_stage1() {
+    gdt_init();
+    idt_init();
+}
+
 void hcf() {
     asm ("cli");
     for (;;) {