wcd937x: Use MICBIAS2 instead of MICBIAS1 for MICB2_VOUT

MICBIAS1 is mapped to MICB2_VOUT. Replace it with
MICBIAS2 as MICBIAS2 is used for mbhc detect.

Change-Id: I23bade728f0c5b9de75d78ccb70e57d74f01adbb
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>