Allow microphone detection on WM8962 to be performed using the interrupt
signal, allowing the detection of both microphone presence and button
presses with a signal singal from the CODEC to CPU.  Currently a 250ms
debounce time is applied to both short circuit and presence detection,
this has not been optimised.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: NLiam Girdwood <lrg@slimlogic.co.uk>