VOL-1941: Use protobufs from the voltha-protos repo, not a copy

- Use protobufs from the voltha-protos repo, not a copy
- Provided option to specify the openolt proto version via make option
- Removed duplicate README.md

Change-Id: Id67714c8119521f8358aaa9245268c47b7e843cf
diff --git a/agent/src/stats_collection.h b/agent/src/stats_collection.h
index ab9f174..8e1c00f 100644
--- a/agent/src/stats_collection.h
+++ b/agent/src/stats_collection.h
@@ -18,7 +18,7 @@
 #ifndef OPENOLT_STATS_COLLECTION_H_
 #define OPENOLT_STATS_COLLECTION_H_
 
-#include <openolt.grpc.pb.h>
+#include <voltha_protos/openolt.grpc.pb.h>
 
 extern "C"
 {