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>
diff --git a/sound/arm/pxa2xx-ac97.c b/sound/arm/pxa2xx-ac97.c
index 5d94118..3a39626 100644
--- a/sound/arm/pxa2xx-ac97.c
+++ b/sound/arm/pxa2xx-ac97.c
@@ -251,18 +251,7 @@
 	},
 };
 
-static int __init pxa2xx_ac97_init(void)
-{
-	return platform_driver_register(&pxa2xx_ac97_driver);
-}
-
-static void __exit pxa2xx_ac97_exit(void)
-{
-	platform_driver_unregister(&pxa2xx_ac97_driver);
-}
-
-module_init(pxa2xx_ac97_init);
-module_exit(pxa2xx_ac97_exit);
+module_platform_driver(pxa2xx_ac97_driver);
 
 MODULE_AUTHOR("Nicolas Pitre");
 MODULE_DESCRIPTION("AC97 driver for the Intel PXA2xx chip");