ASoC: msm: Add mixer control to mute rx device

In answer machine use case, voice rx is muted and
the voice is recorded into file.
The mixer control command is added to mute the rx device.

CRs-Fixed: 338015
Change-Id: I1c71ed4129e8aa2fb7241e2f1fdb77db472235a8
Signed-off-by: Helen Zeng <xiaoyunz@codeaurora.org>