ASoC: wcd-mbhc: Reduce delay in detection for threshold headsets

Certain headsets have threshold on microphone for detection.
Currently mbhc driver takes about 3 to 4 seconds to detect those
headsets. Reduce delay in detection for threshold headsets by
increasing micbias to 2.7v.

Change-Id: I744bafb78560f39806d656c98582d8162fa10dfd
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>