nfs: new subdir Documentation/filesystems/nfs

We're adding enough nfs documentation that it may as well have its own
subdirectory.

Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 27e772c..dc12f41 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -97,7 +97,7 @@
  * @get_name:       find the name for a given inode in a given directory
  * @get_parent:     find the parent of a given directory
  *
- * See Documentation/filesystems/Exporting for details on how to use
+ * See Documentation/filesystems/nfs/Exporting for details on how to use
  * this interface correctly.
  *
  * encode_fh: