ASoC: msm: qdsp6v2: Enable AFE sidetone based on mixer ctl setting

AFE sidetone is currently enabled based on a combination
of mixer control setting and default config in ACDB.
This change will limit enablement to mixer control setting alone.

Change-Id: I038d51177adc3e1da45ea7fdf9386362390f181d
Signed-off-by: Vikram Panduranga <vpandura@codeaurora.org>