media: davinci/vpbe: Fix a typo ("defualt_mode")

Let's spell the variable name correctly.
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

include/media/davinci/vpbe.h

@@ -28,7 +28,7 @@ struct vpbe_output {
 	 */
 	char *subdev_name;
 	/*
-	 * defualt_mode identifies the default timings set at the venc or
+	 * default_mode identifies the default timings set at the venc or
 	 * external encoder.
 	 */
 	char *default_mode;