replace asm volatile("pause") with function

core/spin.c

@@ -1,6 +1,7 @@
 #include <zinnia/atomic.h>
 #include <zinnia/irq.h>
 #include <zinnia/spin.h>
+#include <arch/cpu.h>
 
 void spin_init(struct spinlock* spin) {
     spin->next = 0;
@@ -12,7 +13,7 @@ void spin_lock(struct spinlock* spin) {
     uint32_t my = atomic_fetch_add(&spin->next, 1, ATOMIC_RELAXED);
 
     while (atomic_load(&spin->owner, ATOMIC_ACQUIRE) != my) {
-        asm volatile("pause");
+        arch_cpu_pause();
     }
 }