ASoC: wcd: Remove non-essential current source votings from adc

Zdet current source is enabled for 4 pole aux cable and kept
even after plug removal. This increases voltage for both hph left and
right which causes error in cross-connection detection for subsequent plug
detections. Remove current source enablement from unrequired places.

CRs-Fixed: 2234559
Change-Id: Icffbca88f7a6873c509c91e31b494dd6d5d21cb9
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>