I don't know if there's any built-in function for it - I suspect not, as the suffixes will be different for different languages.
You could do it by creating a table:
daynumber, suffix
1,st
2,nd
3,rd
4,th
...
30,th
31,st
Then create a custom function to pull out the day part of the date, look it up in the table and tack on the relevant suffix.