Kernel: Move Spinlock functions back to arch independent Locking folder

Now that the Spinlock code is not dependent on architectural specific
code anymore, we can move it back to the Locking folder. This also means
that the Spinlock implemenation is now used for the aarch64 kernel.

Kernel/Arch/aarch64/Dummy.cpp

@@ -50,6 +50,14 @@ void Mutex::unlock()
 
 }
 
+// LockRank
+namespace Kernel {
+
+void track_lock_acquire(LockRank) { }
+void track_lock_release(LockRank) { }
+
+}
+
 // Inode
 namespace Kernel {