ALSA: Fix spelling typo in Documentation/DocBook/alsa-driver-api.xml

This patch fix spelling typo found in alsa-driver-api.xml.
It is because this file is generated from comments in source files,
I have to fix source files.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
index 6542c40..fba365a 100644
--- a/sound/core/pcm_dmaengine.c
+++ b/sound/core/pcm_dmaengine.c
@@ -289,7 +289,7 @@
  *
  * The function should usually be called from the pcm open callback. Note that
  * this function will use private_data field of the substream's runtime. So it
- * is not availabe to your pcm driver implementation.
+ * is not available to your pcm driver implementation.
  */
 int snd_dmaengine_pcm_open(struct snd_pcm_substream *substream,
 	struct dma_chan *chan)
@@ -328,7 +328,7 @@
  * This function will request a DMA channel using the passed filter function and
  * data. The function should usually be called from the pcm open callback. Note
  * that this function will use private_data field of the substream's runtime. So
- * it is not availabe to your pcm driver implementation.
+ * it is not available to your pcm driver implementation.
  */
 int snd_dmaengine_pcm_open_request_chan(struct snd_pcm_substream *substream,
 	dma_filter_fn filter_fn, void *filter_data)