ASoC: wcd: Add support to detect special headset

Certain headsets have threshold on mic. Micbias voltage
of 2.8V is required to unlock the microphone in such
headsets. Increase the voltage to 2.8V and check if
the microphone voltage drops in headset range for
special headset.

CRs-Fixed: 662654
Change-Id: Ic53239a0755ca1bc7203c3431e2fa268e9f65737
Signed-off-by: Simmi Pateriya <simmip@codeaurora.org>