configs: set appropriate sidetone volume for headphone

Sidetone volume doesn't fit QRD talos. Lower sidetone volume to
follow tuning guideline.

Change-Id: Ic66631c03057c762553b2011ea615d76acecbb6f
diff --git a/configs/msmsteppe/mixer_paths_qrd.xml b/configs/msmsteppe/mixer_paths_qrd.xml
index f0227c9..6b71170 100644
--- a/configs/msmsteppe/mixer_paths_qrd.xml
+++ b/configs/msmsteppe/mixer_paths_qrd.xml
@@ -2038,7 +2038,7 @@
 
     <path name="sidetone-headphones">
         <path name="sidetone-iir" />
-        <ctl name="IIR0 INP0 Volume" value="54" />
+        <ctl name="IIR0 INP0 Volume" value="40" />
         <ctl name="IIR0 INP0 MUX" value="DEC0" />
         <ctl name="RX INT0 MIX2 INP" value="SRC0" />
         <ctl name="RX INT1 MIX2 INP" value="SRC0" />