USB: convert drivers/input/* to use module_usb_driver()

This converts the drivers in drivers/input/* to use the
module_usb_driver() macro which makes the code smaller and a bit
simpler.

Added bonus is that it removes some unneeded kernel log messages about
drivers loading and/or unloading.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Ville Syrjala <syrjala@sci.fi>
Cc: Henk Vergonet <Henk.Vergonet@gmail.com>
Cc: Alessandro Rubini <rubini@ipvvis.unipv.it>
Cc: Henrik Rydberg <rydberg@euromail.se>
Cc: "Magnus Hörlin" <magnus@alefors.se>
Cc: Chris Moeller <kode54@gmail.c>
Cc: Christoph Fritz <chf.fritz@googlemail.com>
Cc: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Edwin van Vliet <edwin@cheatah.nl>
Cc: Ping Cheng <pingc@wacom.com>
Cc: Eduard Hasenleithner <eduard@hasenleithner.at>
Cc: Alexander Strakh <strakh@ispras.ru>
Cc: Glenn Sommer <gsommer@datanordisk.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/input/joystick/xpad.c b/drivers/input/joystick/xpad.c
index d728875..32bbd4c 100644
--- a/drivers/input/joystick/xpad.c
+++ b/drivers/input/joystick/xpad.c
@@ -1041,18 +1041,7 @@
 	.id_table	= xpad_table,
 };
 
-static int __init usb_xpad_init(void)
-{
-	return usb_register(&xpad_driver);
-}
-
-static void __exit usb_xpad_exit(void)
-{
-	usb_deregister(&xpad_driver);
-}
-
-module_init(usb_xpad_init);
-module_exit(usb_xpad_exit);
+module_usb_driver(xpad_driver);
 
 MODULE_AUTHOR(DRIVER_AUTHOR);
 MODULE_DESCRIPTION(DRIVER_DESC);