davinci-audio: mark user buffer

sound/oss/davinci-audio.c

@@ -588,9 +588,9 @@ audio_write(struct file *file, const char *buffer, size_t count, loff_t * ppos)
  *
  ******************************************************************************/
 static int
-audio_read(struct file *file, char *buffer, size_t count, loff_t * ppos)
+audio_read(struct file *file, char __user *buffer, size_t count, loff_t * ppos)
 {
-	char *buffer0 = buffer;
+	char __user *buffer0 = buffer;
 	audio_state_t *state = file->private_data;
 	audio_stream_t *s = state->input_stream;
 	int chunksize, ret = 0;