Don't refer getfsstat() using .Xr as we don't have man page for it anymore.

Ok from wiz@

lib/libc/gen/getmntinfo.3

@@ -1,4 +1,4 @@
-.\"	$NetBSD: getmntinfo.3,v 1.15 2004/05/05 08:48:36 jdolecek Exp $
+.\"	$NetBSD: getmntinfo.3,v 1.16 2016/06/12 09:42:41 abhinav Exp $
 .\"
 .\" Copyright (c) 1989, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)getmntinfo.3	8.1 (Berkeley) 6/9/93
 .\"
-.Dd April 14, 2004
+.Dd June 2, 2016
 .Dt GETMNTINFO 3
 .Os
 .Sh NAME
@@ -93,7 +93,7 @@ The
 function first appeared in
 .Bx 4.4 .
 It was converted from using
-.Xr getfsstat 2
+.Fn getfsstat
 to
 .Xr getvfsstat 2
 in