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/sound.c b/sound/core/sound.c
index 70ccdab..f002bd9 100644
--- a/sound/core/sound.c
+++ b/sound/core/sound.c
@@ -102,6 +102,9 @@
  * This function increments the reference counter of the card instance
  * if an associated instance with the given minor number and type is found.
  * The caller must call snd_card_unref() appropriately later.
+ *
+ * Return: The user data pointer if the specified device is found. %NULL
+ * otherwise.
  */
 void *snd_lookup_minor_data(unsigned int minor, int type)
 {
@@ -261,7 +264,7 @@
  * Registers an ALSA device file for the given card.
  * The operators have to be set in reg parameter.
  *
- * Returns zero if successful, or a negative error code on failure.
+ * Return: Zero if successful, or a negative error code on failure.
  */
 int snd_register_device_for_dev(int type, struct snd_card *card, int dev,
 				const struct file_operations *f_ops,
@@ -339,7 +342,7 @@
  * Unregisters the device file already registered via
  * snd_register_device().
  *
- * Returns zero if sucecessful, or a negative error code on failure
+ * Return: Zero if successful, or a negative error code on failure.
  */
 int snd_unregister_device(int type, struct snd_card *card, int dev)
 {