ASoC: msm8960: Fix mbhc multi button detection

If mic bias voltage is higher than vddio voltage, scale up the measured
voltage when a button is pressed during playback in order to use ACDB
button voltage range.
Default mic bias of mbhc voltage has changed from 1.8v to 2.7v,
so fix default values with re-calibrated ones based on 2.7v mic bias
voltage.

CRs-fixed: 336279
Change-Id: Iff99ffc91e37c5fe477d330f81dfa2e8383732da
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>