audio policy: move device_category type outside volume class

This patch prepares the removal of hard coded volume tables by
moving outside volume class the device_category enumeration.

Change-Id: Ic712377898276a39bb782ac0bc7f793cdd7fa8bd
Signed-off-by: François Gaffie <francois.gaffie@intel.com>
diff --git a/services/audiopolicy/engineconfigurable/interface/AudioPolicyPluginInterface.h b/services/audiopolicy/engineconfigurable/interface/AudioPolicyPluginInterface.h
index 74daba5..43d441e 100755
--- a/services/audiopolicy/engineconfigurable/interface/AudioPolicyPluginInterface.h
+++ b/services/audiopolicy/engineconfigurable/interface/AudioPolicyPluginInterface.h
@@ -116,7 +116,7 @@
      * @return true if the strategy were set correclty for this stream, false otherwise.
      */
     virtual bool setVolumeProfileForStream(const audio_stream_type_t &stream,
-                                           Volume::device_category category,
+                                           device_category category,
                                            const VolumeCurvePoints &points) = 0;
 
     /**