[POWERPC] Restore copyright notice in arch/powerpc/kernel/fpu.S

This code got moved from head.S but the copyright notice on head.S didn't
get transferred with it.  Noticed by Cort Dougan <cort@fsmlabs.com>.

Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/fpu.S

@@ -2,6 +2,11 @@
  *  FPU support code, moved here from head.S so that it can be used
  *  by chips which use other head-whatever.S files.
  *
+ *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *    Copyright (C) 1996 Cort Dougan <cort@cs.nmt.edu>
+ *    Copyright (C) 1996 Paul Mackerras.
+ *    Copyright (C) 1997 Dan Malek (dmalek@jlc.net).
+ *
  *  This program is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public License
  *  as published by the Free Software Foundation; either version