[ALSA] Fix DocBook warnings

PCM Midlevel,RawMidi Midlevel
Fix DocBook warnings.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index d705ec7..4f4b410 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -1109,7 +1109,7 @@
 /**
  * snd_rawmidi_transmit - copy from the buffer to the device
  * @substream: the rawmidi substream
- * @buf: the buffer pointer
+ * @buffer: the buffer pointer
  * @count: the data size to transfer
  * 
  * Copies data from the buffer to the device and advances the pointer.