milan-avb: lock: make it lockable:

1. The period calls were added to handle timeouts.
2. Handle the case where lock must be unlocked after 60s if the
   controller owning the locked does not release it.

src/modules/module-avb/aecp-aem-cmds-resps/cmd-lock-entity.h

@@ -12,6 +12,15 @@
 
 #include <stdint.h>
 
+/**
+ * @brief Checks whether the Milan entity lock has expired and releases it.
+ *
+ * Called once per second from the AECP periodic handler.  If the lock is
+ * active and its timeout (set at lock time) is earlier than @p now, the
+ * lock is cleared.
+ */
+void handle_cmd_lock_entity_expired_milan_v12(struct aecp *aecp, int64_t now);
+
 /**
  * @brief Command handling will generate the response for the lock command
  */