MTP: Partial implementation of the GetObjectPropList command

In this initial implementation we only support fetching one property at a time.
Support depth = 0 (single object) or depth = 1 (all objects in a directory)
Reimplemented GetObjectPropValue on top of GetObjectPropList, since the former
is a special case of the latter.

Change-Id: Ia76ee61741d6ee3902b5c5d9fc094cf86dfaf650
Signed-off-by: Mike Lockwood <lockwood@google.com>
diff --git a/media/mtp/MtpServer.h b/media/mtp/MtpServer.h
index 68a6564..e65ddb0 100644
--- a/media/mtp/MtpServer.h
+++ b/media/mtp/MtpServer.h
@@ -93,6 +93,7 @@
     MtpResponseCode     doGetDevicePropValue();
     MtpResponseCode     doSetDevicePropValue();
     MtpResponseCode     doResetDevicePropValue();
+    MtpResponseCode     doGetObjectPropList();
     MtpResponseCode     doGetObjectInfo();
     MtpResponseCode     doGetObject();
     MtpResponseCode     doSendObjectInfo();