Revert "Remove USE_XML_AUDIO_POLICY_CONF build flag"

This reverts commit f0ecc2087d01fb9f64217f23e64261f75e01d525.

Reason for revert: Buildcop

Change-Id: I7696c27210778a02456e051679b47e47dec119bb
diff --git a/device-common.mk b/device-common.mk
index df15455..525ae8d 100644
--- a/device-common.mk
+++ b/device-common.mk
@@ -221,6 +221,7 @@
         $(LOCAL_PATH)/p2p_supplicant_overlay.conf:$(TARGET_COPY_OUT_VENDOR)/etc/wifi/p2p_supplicant_overlay.conf
 
 # audio policy configuration
+USE_XML_AUDIO_POLICY_CONF := 1
 PRODUCT_COPY_FILES += \
     device/linaro/hikey/audio/audio_policy_configuration.xml:$(TARGET_COPY_OUT_VENDOR)/etc/audio_policy_configuration.xml \
     frameworks/av/services/audiopolicy/config/a2dp_audio_policy_configuration.xml:$(TARGET_COPY_OUT_VENDOR)/etc/a2dp_audio_policy_configuration.xml \