ASoC: wcd934x: Add support for voltage scaling

WCD934X audio codec supports static voltage scaling (SVS) mode, which
puts the codec into lowest power state. The codec has different power
states (SVS2, SVS and Nominal). Add support in codec driver to vote
for SVS when audio usecases are enabled and remove vote for SVS when
audio usecases are disabled. The codec driver only votes for SVS or
no SVS and the hardware internally manages to go into Nominal mode.

CRs-Fixed: 1049012
Change-Id: I6f66d3136e3c49da54f5919184bc113267105463
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>