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/src/Engine.cpp b/services/audiopolicy/engineconfigurable/src/Engine.cpp
index 733cdf6..32341ec 100755
--- a/services/audiopolicy/engineconfigurable/src/Engine.cpp
+++ b/services/audiopolicy/engineconfigurable/src/Engine.cpp
@@ -116,7 +116,7 @@
 }
 
 bool Engine::setVolumeProfileForStream(const audio_stream_type_t &streamType,
-                                       Volume::device_category deviceCategory,
+                                       device_category deviceCategory,
                                        const VolumeCurvePoints &points)
 {
     Stream *stream = getFromCollection<audio_stream_type_t>(streamType);
@@ -199,9 +199,9 @@
     return element->template set<Property>(property) == NO_ERROR;
 }
 
-float Engine::volIndexToDb(Volume::device_category category,
-                             audio_stream_type_t streamType,
-                             int indexInUi)
+float Engine::volIndexToDb(device_category category,
+                           audio_stream_type_t streamType,
+                           int indexInUi)
 {
     Stream *stream = getFromCollection<audio_stream_type_t>(streamType);
     if (stream == NULL) {