ASoC: msm8x10-wcd: Pull TX2 to micbias whenever micbias is enabled

It is noticed that the headset mic has a buzz whenever micbias is
enabled. To reduce this buzz, always pull up the TX2 (headset)
microphone front end to micbias.

CRs-fixed: 526901
Change-Id: Id007a4c34c68aea0d0e01743d3e7aa8ca09fd5f7
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>