ALSA: convert sound/* to use module_platform_driver()

This patch converts the drivers in sound/* 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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/sh/sh_dac_audio.c

@@ -441,15 +441,4 @@ static struct platform_driver driver = {
 	},
 };
 
-static int __init sh_dac_init(void)
-{
-	return platform_driver_register(&driver);
-}
-
-static void __exit sh_dac_exit(void)
-{
-	platform_driver_unregister(&driver);
-}
-
-module_init(sh_dac_init);
-module_exit(sh_dac_exit);
+module_platform_driver(driver);