ASoC: Convert CODEC drivers to module_platform_driver

Factors out a bit of boilerplate.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/wm8400.c b/sound/soc/codecs/wm8400.c
index 07d84a8..a1173eb 100644
--- a/sound/soc/codecs/wm8400.c
+++ b/sound/soc/codecs/wm8400.c
@@ -1477,17 +1477,7 @@
 	.remove = __devexit_p(wm8400_remove),
 };
 
-static __init int wm8400_init(void)
-{
-	return platform_driver_register(&wm8400_codec_driver);
-}
-module_init(wm8400_init);
-
-static __exit void wm8400_exit(void)
-{
-	platform_driver_unregister(&wm8400_codec_driver);
-}
-module_exit(wm8400_exit);
+module_platform_driver(wm8400_codec_driver);
 
 MODULE_DESCRIPTION("ASoC WM8400 driver");
 MODULE_AUTHOR("Mark Brown");