Is there any AWS RDS Utility to Manage Master Slave mysql db with read write splitting?
AWS does not have a service that provides this.  

Transparent, intelligent read/write splitting is a Hard Problem&trade; because there are so many details that can go wrong, such as queries that use user-defined variables, which aren't deterministic unless the state of the variables is maintained across multiple connections... inconsistent reads and read-after-write due to replication lag... and many others.

The only solutions for now are third-party products like Maxscale and ProxySQL, unless you are using a connector library or ORM that manages such things for you (assuming such things exist).