ALSA: Fix typos in alsa-driver-api.xml

This patch fixed 2 typos in DocBook/alsa-driver-api.xml.
It is because this file is generated by make xmldocs,
I have to fix typos within source files.

Signed-off-by: Masanari Iida <standby24x7@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 01a5e05..10b5d1a 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -954,7 +954,7 @@
  *
  * The state of each stream is then changed to the given state unconditionally.
  *
- * Return: Zero if succesful, or a negative error code.
+ * Return: Zero if successful, or a negative error code.
  */
 int snd_pcm_stop(struct snd_pcm_substream *substream, snd_pcm_state_t state)
 {