doc(PubSub): Update README_pubsub_TSN.txt
doc(PubSub): Update README_pubsub_TSN.txt

 - Update README_pubsub_TSN.txt with respect to refactoring of XDP

Change-Id: I2179c3a30c9571006818c3260d08bb8fbfd0a747

jpfr/open62541,open62541/open62541,open62541/open62541,StalderT/open62541,JGrothoff/open62541,jpfr/open62541,open62541/open62541,StalderT/open62541,open62541/open62541,jpfr/open62541,jpfr/open62541,JGrothoff/open62541,StalderT/open62541,JGrothoff/open62541,StalderT/open62541,JGrothoff/open62541