ASoC: Implement interrupt driven microphone detection for WM8903

Support use of the WM8903 IRQ for reporting of microphone presence
and short detection.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
diff --git a/include/sound/wm8903.h b/include/sound/wm8903.h
index 49bb1a8..b4a0db23 100644
--- a/include/sound/wm8903.h
+++ b/include/sound/wm8903.h
@@ -241,6 +241,8 @@
 	 */
 	u16 micdet_cfg;
 
+	int micdet_delay;      /* Delay after microphone detection (ms) */
+
 	u32 gpio_cfg[5];       /* Default register values for GPIO pin mux */
 };