ASoC: wcd9xxx: Use lower voltage micbias for plug type determination

Enable current source during plug type determination
and use it for measuring mic voltages to minimize pop
noise resulting from higher voltage of mic bias.

Change-Id: I4e67a64dfbb3952c0bfebebb08eb030ce12ed8d0
CRs-fixed: 485047
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>