ASoC: Add kerneldoc for jack_status_check callback

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>

include/sound/soc.h

@@ -437,6 +437,9 @@ struct snd_soc_jack_zone {
  * @invert:       report presence in low state
  * @debouce_time: debouce time in ms
  * @wake:	  enable as wake source
+ * @jack_status_check: callback function which overrides the detection
+ *		       to provide more complex checks (eg, reading an
+ *		       ADC).
  */
 #ifdef CONFIG_GPIOLIB
 struct snd_soc_jack_gpio {