MTP: Add support for device property changed events

Also fixed bug in MtpProperty::write() for device properties

Bug: 7342482
Change-Id: If0099095d101409d131564e55b1939895c69c202
diff --git a/media/mtp/MtpServer.h b/media/mtp/MtpServer.h
index dfa8258..b3a11e0 100644
--- a/media/mtp/MtpServer.h
+++ b/media/mtp/MtpServer.h
@@ -104,6 +104,7 @@
 
     void                sendObjectAdded(MtpObjectHandle handle);
     void                sendObjectRemoved(MtpObjectHandle handle);
+    void                sendDevicePropertyChanged(MtpDeviceProperty property);
 
 private:
     void                sendStoreAdded(MtpStorageID id);