nfs: rename the nfs_async_rename_done tracepoint

We do async renames in other cases besides sillyrenames now. This
tracepoint name is now misleading.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>