Enable Cereal class versioning

Cereal class versioning helps to handle data de-serialization
across different class versions that differ in the way, a particular
data is serialized.

For more reading, refer Cereal official documentation;
http://uscilab.github.io/cereal/serialization_functions.html

Change-Id: Ic5d01090b7a7679ef2bf638da786abbd033007bc
Signed-off-by: Vishwanatha Subbanna <vishwa@linux.vnet.ibm.com>
diff --git a/host_state_manager.cpp b/host_state_manager.cpp
index 8debe8a..884372d 100644
--- a/host_state_manager.cpp
+++ b/host_state_manager.cpp
@@ -16,6 +16,8 @@
 #include "host_state_manager.hpp"
 #include "config.h"
 
+// Register class version with Cereal
+CEREAL_CLASS_VERSION(phosphor::state::manager::Host, CLASS_VERSION);
 
 namespace phosphor
 {