Purpose of this virtual Detection pin is to keep codec bias on whenever the
GPIO or jack detection features are needed.

Jack detection needs a mic bias so machine drivers can construct a following
route for instance for keeping the path and codec bias on:

"Input Jack" -> "Mic Bias xV" -> "Detection" -> detection block inside codec.

For the GPIO the machine driver can force the pin on with
snd_soc_dapm_force_enable_pin.
Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>