USB: fix up license wording on some of my usb-serial drivers

Also update the copyright date on the pl2303 driver, as it was out of date.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/visor.c

@@ -5,9 +5,9 @@
  *	Copyright (C) 1999 - 2004
  *	    Greg Kroah-Hartman (greg@kroah.com)
  *
- *	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 2 of the License.
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License version
+ *	2 as published by the Free Software Foundation.
  *
  * See Documentation/usb/usb-serial.txt for more information on using this driver
  *