ALSA: use subsys_initcall for sound core instead of module_init

This is needed for built-in drivers which are built before the sound directory,
like thinkpad_acpi.

Otherwise, registering a card fails.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/sound_core.c b/sound/sound_core.c
index dbca7c9..7c2d677 100644
--- a/sound/sound_core.c
+++ b/sound/sound_core.c
@@ -61,7 +61,7 @@
 	class_destroy(sound_class);
 }
 
-module_init(init_soundcore);
+subsys_initcall(init_soundcore);
 module_exit(cleanup_soundcore);