Follow-up to r1645586. Fix build.

* subversion/libsvn_fs_x/tree.c
  (cache_lookup_last_path,
   try_match_last_node): Update used type and called function names to FSX.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1645587 13f79535-47bb-0310-9956-ffa450edef68