From an Infinispan configuration perspective, nothing needs changing. The Infinispan provider still uses the same base configuration by default. Transactional configuration happens within the cache provider itself and it's here where the Infinispan is configured with Hibernate's transaction manager and where Infinispan is configured to participate as a JTA synchronization. This is the default configuration, so from an user perspective, there's nothing you have to do to take advantage of this new change.
However, you can always switch back to previous behaviour where Infinispan interacted as an XA resource via a dedicated Hibernate property called hibernate.cache.infinispan.use_synchronization
By default this property is set to true. If you set it false, Infinispan will interact with the transaction manager as an XA resource.
For more detailed information, check the "Using Infinispan As JPA Hibernate Second Level Cache Provider" wiki.