CMParts: Add volume button call answer switch

Change-Id: I1231a2f13360ed8ba1f2ab929c7791dd4d32522f
diff --git a/res/xml/button_settings.xml b/res/xml/button_settings.xml
index c587fca..a4b4c9f 100644
--- a/res/xml/button_settings.xml
+++ b/res/xml/button_settings.xml
@@ -257,6 +257,12 @@
             android:defaultValue="false" />
 
         <cyanogenmod.preference.CMSystemSettingSwitchPreference
+            android:key="volume_answer_call"
+            android:title="@string/volume_answer_call_title"
+            android:summary="@string/volume_answer_call_summary"
+            android:defaultValue="false" />
+
+        <cyanogenmod.preference.CMSystemSettingSwitchPreference
             android:key="volbtn_music_controls"
             android:title="@string/volbtn_music_controls_title"
             android:summary="@string/volbtn_music_controls_summary"