PMM and liballoc port

kernel/sync/spin_lock.c

@@ -0,0 +1,12 @@
+#include <libk/std.h>
+#include <sys/spin_lock.h>
+#include <sync/spin_lock.h>
+
+void spin_lock(spin_lock_t *sl) {
+  while (atomic_flag_test_and_set_explicit(sl, memory_order_acquire))
+    spin_lock_relax();
+}
+
+void spin_unlock(spin_lock_t *sl) {
+  atomic_flag_clear_explicit(sl, memory_order_release);
+}