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/vmaster.c b/sound/core/vmaster.c
index 8575861..55c9d8c 100644
--- a/sound/core/vmaster.c
+++ b/sound/core/vmaster.c
@@ -362,8 +362,7 @@
  * @name: name string of the control element to create
  * @tlv: optional TLV int array for dB information
  *
- * Creates a virtual matster control with the given name string.
- * Returns the created control element, or NULL for errors (ENOMEM).
+ * Creates a virtual master control with the given name string.
  *
  * After creating a vmaster element, you can add the slave controls
  * via snd_ctl_add_slave() or snd_ctl_add_slave_uncached().
@@ -372,6 +371,8 @@
  * for dB scale of the master control.  It should be a single element
  * with #SNDRV_CTL_TLVT_DB_SCALE, #SNDRV_CTL_TLV_DB_MINMAX or
  * #SNDRV_CTL_TLVT_DB_MINMAX_MUTE type, and should be the max 0dB.
+ *
+ * Return: The created control element, or %NULL for errors (ENOMEM).
  */
 struct snd_kcontrol *snd_ctl_make_virtual_master(char *name,
 						 const unsigned int *tlv)
@@ -423,6 +424,8 @@
  *
  * Adds the given hook to the vmaster control element so that it's called
  * at each time when the value is changed.
+ *
+ * Return: Zero.
  */
 int snd_ctl_add_vmaster_hook(struct snd_kcontrol *kcontrol,
 			     void (*hook)(void *private_data, int),