Read memory map tags from multiboot

src/kernel/include/multiboot.h

@@ -1,12 +1,16 @@
 #pragma once
 #include <stdint.h>
+#include <stddef.h>
 struct kernel_boot_data_st
 {
   int multiboot_version;
   char *bootloader;
   char *commandline;
+  size_t mmap_size;
+  void *mmap;
 };
 
 extern struct kernel_boot_data_st kernel_boot_data;
 
 int multiboot_init(uint64_t magic, void *mboot_info);
+int multiboot_get_memory_area(size_t count, uintptr_t *start, uintptr_t *end, uint32_t *type);