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>
diff --git a/drivers/watchdog/riowd.c b/drivers/watchdog/riowd.c
index 109b533..c7e17ce 100644
--- a/drivers/watchdog/riowd.c
+++ b/drivers/watchdog/riowd.c
@@ -247,15 +247,4 @@
 	.remove		= __devexit_p(riowd_remove),
 };
 
-static int __init riowd_init(void)
-{
-	return platform_driver_register(&riowd_driver);
-}
-
-static void __exit riowd_exit(void)
-{
-	platform_driver_unregister(&riowd_driver);
-}
-
-module_init(riowd_init);
-module_exit(riowd_exit);
+module_platform_driver(riowd_driver);