Make checkpointing work on ext4

Test: All tests pass
Change-Id: I2a6cdf1edfe752f4633e1931e75d18659653938c
diff --git a/Checkpoint.h b/Checkpoint.h
index 8449956..81fba99 100644
--- a/Checkpoint.h
+++ b/Checkpoint.h
@@ -34,6 +34,8 @@
 
 bool cp_prepareDriveForCheckpoint(const std::string& mountPoint);
 
+bool cp_restoreCheckpoint(const std::string& mountPoint);
+
 bool cp_markBootAttempt();
 
 }  // namespace vold