ALSA: Clean up snd_device_*() codes

A few code cleanups and optimizations.  In addition, drop
snd_device_disconnect() that isn't used at all, and drop the return
values from snd_device_free*().

Another slight difference by this change is that now the device state
will become always SNDRV_DEV_REGISTERED no matter whether dev_register
ops is present or not.  It's for better consistency.  There should be
no impact for the current tree, as the state isn't checked.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/core.h b/include/sound/core.h
index f1e41f4..aac9a85 100644
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -309,10 +309,9 @@
 		   void *device_data, struct snd_device_ops *ops);
 int snd_device_register(struct snd_card *card, void *device_data);
 int snd_device_register_all(struct snd_card *card);
-int snd_device_disconnect(struct snd_card *card, void *device_data);
 int snd_device_disconnect_all(struct snd_card *card);
-int snd_device_free(struct snd_card *card, void *device_data);
-int snd_device_free_all(struct snd_card *card);
+void snd_device_free(struct snd_card *card, void *device_data);
+void snd_device_free_all(struct snd_card *card);
 
 /* isadma.c */