Add a mechanism for Audio Feeding Parameters negotiation

Previously, the Audio Feeding Parameters between the Media Framework
and A2DP were hard-coded: 44.1 KHz sample rate, 16-bits per sample, Stereo.
Now the Media Framework queries A2DP, and uses the returned values.

Bug: b/30958229
Test: Manual testing: A2DP streaming to headphones. TestTracker/68727
Change-Id: Ib86035814c49f773b7ed3d64da334ca9ea87eb14
diff --git a/services/audiopolicy/config/a2dp_audio_policy_configuration.xml b/services/audiopolicy/config/a2dp_audio_policy_configuration.xml
index ced7463..7bcab5c 100644
--- a/services/audiopolicy/config/a2dp_audio_policy_configuration.xml
+++ b/services/audiopolicy/config/a2dp_audio_policy_configuration.xml
@@ -2,11 +2,7 @@
 <!-- A2dp Audio HAL Audio Policy Configuration file -->
 <module name="a2dp" halVersion="2.0">
     <mixPorts>
-        <mixPort name="a2dp output" role="source">
-            <profile name="" format="AUDIO_FORMAT_PCM_16_BIT"
-                     samplingRates="44100"
-                     channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
-        </mixPort>
+        <mixPort name="a2dp output" role="source"/>
         <mixPort name="a2dp input" role="sink">
             <profile name="" format="AUDIO_FORMAT_PCM_16_BIT"
                      samplingRates="44100,48000"