watchdog: convert drivers/watchdog/* to use module_platform_driver()

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

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: Nicolas Thill <nico@openwrt.org>
Cc: Florian Fainelli <florian@openwrt.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Paul Cercueil <paul@crapouillou.net>
Cc: Marc Zyngier <maz@misterjones.org>
Cc: Wan ZongShun <mcuos.com@gmail.com>
Cc: Alejandro Cabrera <aldaya@gmail.com>
Cc: "George G. Davis" <gdavis@mvista.com>
Cc: Sylver Bruneau <sylver.bruneau@googlemail.com>
Cc: Vitaly Wool <vital@embeddedalley.com>
Cc: Mika Westerberg <mika.westerberg@iki.fi>
Cc: Timo Kokkonen <timo.t.kokkonen@nokia.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/ar7_wdt.c

@@ -353,15 +353,4 @@ static struct platform_driver ar7_wdt_driver = {
 	},
 };
 
-static int __init ar7_wdt_init(void)
-{
-	return platform_driver_register(&ar7_wdt_driver);
-}
-
-static void __exit ar7_wdt_cleanup(void)
-{
-	platform_driver_unregister(&ar7_wdt_driver);
-}
-
-module_init(ar7_wdt_init);
-module_exit(ar7_wdt_cleanup);
+module_platform_driver(ar7_wdt_driver);