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/common/include/Volume.h b/services/audiopolicy/common/include/Volume.h
index 712f7a7..d091179 100755
--- a/services/audiopolicy/common/include/Volume.h
+++ b/services/audiopolicy/common/include/Volume.h
@@ -30,6 +30,17 @@
     float mDBAttenuation;
 };
 
+/**
+ * device categories used for volume curve management.
+ */
+enum device_category {
+    DEVICE_CATEGORY_HEADSET,
+    DEVICE_CATEGORY_SPEAKER,
+    DEVICE_CATEGORY_EARPIECE,
+    DEVICE_CATEGORY_EXT_MEDIA,
+    DEVICE_CATEGORY_CNT
+};
+
 class Volume
 {
 public:
@@ -50,17 +61,6 @@
     };
 
     /**
-     * device categories used for volume curve management.
-     */
-    enum device_category {
-        DEVICE_CATEGORY_HEADSET,
-        DEVICE_CATEGORY_SPEAKER,
-        DEVICE_CATEGORY_EARPIECE,
-        DEVICE_CATEGORY_EXT_MEDIA,
-        DEVICE_CATEGORY_CNT
-    };
-
-    /**
      * extract one device relevant for volume control from multiple device selection
      *
      * @param[in] device for which the volume category is associated