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/pcm_native.c b/sound/core/pcm_native.c
index 71ae86c..5bce915 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -898,6 +898,8 @@
 /**
  * snd_pcm_start - start all linked streams
  * @substream: the PCM substream instance
+ *
+ * Return: Zero if successful, or a negative error code.
  */
 int snd_pcm_start(struct snd_pcm_substream *substream)
 {
@@ -951,6 +953,8 @@
  * @state: PCM state after stopping the stream
  *
  * The state of each stream is then changed to the given state unconditionally.
+ *
+ * Return: Zero if succesful, or a negative error code.
  */
 int snd_pcm_stop(struct snd_pcm_substream *substream, snd_pcm_state_t state)
 {
@@ -965,6 +969,8 @@
  *
  * After stopping, the state is changed to SETUP.
  * Unlike snd_pcm_stop(), this affects only the given stream.
+ *
+ * Return: Zero if succesful, or a negative error code.
  */
 int snd_pcm_drain_done(struct snd_pcm_substream *substream)
 {
@@ -1098,6 +1104,9 @@
  * @substream: the PCM substream
  *
  * After this call, all streams are changed to SUSPENDED state.
+ *
+ * Return: Zero if successful (or @substream is %NULL), or a negative error
+ * code.
  */
 int snd_pcm_suspend(struct snd_pcm_substream *substream)
 {
@@ -1120,6 +1129,8 @@
  * @pcm: the PCM instance
  *
  * After this call, all streams are changed to SUSPENDED state.
+ *
+ * Return: Zero if successful (or @pcm is %NULL), or a negative error code.
  */
 int snd_pcm_suspend_all(struct snd_pcm *pcm)
 {
@@ -1343,6 +1354,8 @@
  * snd_pcm_prepare - prepare the PCM substream to be triggerable
  * @substream: the PCM substream instance
  * @file: file to refer f_flags
+ *
+ * Return: Zero if successful, or a negative error code.
  */
 static int snd_pcm_prepare(struct snd_pcm_substream *substream,
 			   struct file *file)