sparc: update copyright in piggyback.c

Update copyright info in piggyback.c to include
info from piggyback_64.c.
Include my own copyright too.

Signed-off-by: Sam Ravnborg <[e-mail]>
Cc: Josip Rodin <[e-mail]>
Cc: Jakub Jelinek <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

arch/sparc/boot/piggyback.c

···
    Simple utility to make a single-image install kernel with initial ramdisk
    for Sparc tftpbooting without need to set up nfs.
 
-   Copyright (C) 1996 Jakub Jelinek ([e-mail])
+   Copyright (C) 1996,1997 Jakub Jelinek ([e-mail])
    Pete Zaitcev <[e-mail]> endian fixes for cross-compiles, 2000.
+   Copyright (C) 2011 Sam Ravnborg <[e-mail]>
 
    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