Add ARM spinlock

os/sync/spinlock.h

@@ -0,0 +1,16 @@
+#ifndef SPINLOCK_H
+#define SPINLOCK_H
+
+#include <stdint.h>
+
+// Spinlock
+typedef struct {
+    volatile int lock;
+} Spinlock;
+
+void spinlock_init(Spinlock *spinlock);
+void spinlock_acquire(Spinlock *spinlock);
+void spinlock_release(Spinlock *spinlock);
+
+
+#endif