feat: some clean up and validation of multiboot header

kernel/libk/libk.c

@@ -17,12 +17,12 @@ void k_wait_for_interrupt() {
 
 void noreturn k_panics(const char *msg) {
     // todo this is not printed
-    kprint(msg);
+    kprint_sync(msg);
     k_panic();
 }
 
 void noreturn k_panic() {
-    kprint("PANIC!");
+    kprint_sync("PANIC!");
     while (true) {
         __asm__ __volatile__("cli;"
                              "hlt;");