audio: Add configuration for surround sound

Bug: 116356348
Test: xmllint --noout --xinclude --schema \
  hardware/interfaces/audio/4.1/config/audio_policy_configuration.xsd \
  frameworks/av/services/audiopolicy/config/audio_policy_configuration.xml

Change-Id: Ib8d84b950f439c2ebed181385b41a83556976e60