ASoC: wcd9xxx: Avoid micbias glitches during audio playback

During audio playback over headset, micbias output is switched
to vddio and it's parameters are programmed so that it will do
button polling with a voltage equal to vddio (1.8v). It is observed
that during this polling interval there is a drop in micbias
voltage which would cause issues with button press. Avoid this
voltage drop by disabling mbhc micbias when vddio switch is enabled.

CRs-Fixed: 705060
Change-Id: I0c2f6a0224760aef1f8e51b1ae34c77fc9863b52
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>