ALSA: add/change some comments describing function return values

script/kernel-doc reports the following type of warnings (when run in verbose
mode):

Warning(sound/core/init.c:152): No description found for return value of
'snd_card_create'

To fix that:
- add missing descriptions of function return values
- use "Return:" sections to describe those return values

Along the way:
- complete some descriptions
- fix some typos

Signed-off-by: Yacine Belkadi <yacine.belkadi.1@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/hwdep.c b/sound/core/hwdep.c
index 3f7f662..d105073 100644
--- a/sound/core/hwdep.c
+++ b/sound/core/hwdep.c
@@ -356,7 +356,7 @@
  * The callbacks (hwdep->ops) must be set on the returned instance
  * after this call manually by the caller.
  *
- * Returns zero if successful, or a negative error code on failure.
+ * Return: Zero if successful, or a negative error code on failure.
  */
 int snd_hwdep_new(struct snd_card *card, char *id, int device,
 		  struct snd_hwdep **rhwdep)