dsp: fix 2nd channel mute in VPRx out for Stereo EC ref

In Stereo EC reference, mute is observed in VPRx output
of 2nd channel when only speaker device uses custom MFC topology.

When handset and speaker use the same custom topology, issue is not
observed. Because when DSP VPRx module creates the
custom topology with handset configuration (1 channel and
center channel mapping) and device switch to speaker occurs
MFC conversion from center to left and right channels is successful.

But in case where handset uses default topology, when device
switch to speaker occurs, VPRx creates the custom topology
with speaker configuration(2 channels and left mapping). So,
when MFC config is received, only left->left mapping is done which
leads to mute in right channel.

Fix is to send the channel mixer configuration to MFC module
so that both left->left and left->right mapping is done.

CRs-Fixed: 2102374
Change-Id: If9be09866615e6623e78f48b9841eb068c825992
Signed-off-by: Aditya Bavanari <abavanar@codeaurora.org>