ASoC: wcd9335: update VBat ADC configuration for v2.0

The register write sequence for ADC configuration on WCD9335
v2.0 codec is different from the previous version of the
codec. Update corresponding function to follow the updated
register write sequence and arrange those in separate
functions.

Change-Id: Ie1a3c5491e71119b4e2f116ca0026c0f16e74513
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>