ASoC: wcd938x: Reduce glitch during headset record

Enable ADC Mode and tx channel cfg as part of enable_adc.
This should be enabled before enabling bolero dec so as
to reduce glitch or saturation for headset.

Change-Id: I94045d0c3b7b96744afb9e6a9a3eecf0abc5a55f
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>