sound: add missing pcm kernel-doc

Fix alsa kernel-doc warning in linux-next:

Warning(linux-next-20081016//sound/core/pcm_misc.c:327): No description found for parameter 'samples'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/pcm_misc.c b/sound/core/pcm_misc.c
index 89b7f54..ea2bf82 100644
--- a/sound/core/pcm_misc.c
+++ b/sound/core/pcm_misc.c
@@ -319,6 +319,7 @@
 /**
  * snd_pcm_format_size - return the byte size of samples on the given format
  * @format: the format to check
+ * @samples: sampling rate
  *
  * Returns the byte size of the given samples for the format, or a
  * negative error code if unknown format.