Add vdc checkpoint restoreCheckpointPart

Restores the first n entries of a checkpoint. Allows automated testing
of interrupted restores.

Test: vdc checkpoint restoreCheckpoint [device] [n]
Change-Id: I47570e8eba0bc3c6549a04a33600df05d393990b
diff --git a/VoldNativeService.h b/VoldNativeService.h
index 7db3e5c..954b8ae 100644
--- a/VoldNativeService.h
+++ b/VoldNativeService.h
@@ -127,6 +127,7 @@
     binder::Status commitChanges();
     binder::Status prepareCheckpoint();
     binder::Status restoreCheckpoint(const std::string& mountPoint);
+    binder::Status restoreCheckpointPart(const std::string& mountPoint, int count);
     binder::Status markBootAttempt();
     binder::Status abortChanges();
     binder::Status supportsCheckpoint(bool* _aidl_return);