ASoC: msm8x10-wcd: Do not disable micbias when TX path is ON

Insert headset after initiating voice call and then force switch
to speaker mode.In this case if headset is removed, we are disabling
micbias which is resulting in TX path mute.So check whether TX path is
active before powering down micbias

CRs-Fixed: 593607
Change-Id: Iddc3780e7ed9806499cb79e1159d4b43d63136a3
Signed-off-by: Simmi Pateriya <simmip@codeaurora.org>