ASoC: msm: Support independent left-right channel volume control

The current volume sent to DSP is averaged between left and
right channels. As a result with volume level as zero on one
channel and non zero on the other channel results to playback on
both channels. Add support to send left and right volumes to DSP

Change-Id: Icc5f182d138c841607ea356ec37a7f78b4ba770d
CRs-Fixed: 449284
Signed-off-by: Subhash Chandra Bose Naripeddy <snariped@codeaurora.org>
Signed-off-by: Jay Wang <jaywang@codeaurora.org>