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/fs/nfs/Kconfig b/fs/nfs/Kconfig
index 2a77bc2..59e5673 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -90,7 +90,7 @@
 	  If you want your system to mount its root file system via NFS,
 	  choose Y here.  This is common practice for managing systems
 	  without local permanent storage.  For details, read
-	  <file:Documentation/filesystems/nfsroot.txt>.
+	  <file:Documentation/filesystems/nfs/nfsroot.txt>.
 
 	  Most people say N here.